View source for Wikipedia:Citation underkill

{{essay|WP:UNDERKILL|WP:UNDERCITE|WP:UNDERREF|interprets=the [[Wikipedia:Verifiability|Verifiable policies]] and the [[Wikipedia:Citing sources|Citing sources guidelines]]}}
{{nutshell|It is always best to cite each idea or concept, even those that may seem obvious: as you may be wrong; or they may be less-than obvious to others. Instead of putting accuracy, neutrality and verifiability at stake, simply source all your statements.}}
[[Image:Homère, Odyssée, Fondation Martin Bodmer (Incunable).jpg|thumb|275px|A single [[Wikipedia:Reliable sources|good]] source is often enough to support a statement; however, it is best for statements to be sourced than to go unsupported.|alt=A single reliable source is often enough to support a statement—however, it is best for statements to be sourced than to go unsupported.]]

The quality of Wikipedia improves by making an effort to cite each statement; our material is required by the [[Wikipedia:Verifiability]] policy to be verifiable with [[Wikipedia:Identifying reliable sources|reliable sources]]. Maintaining article standards is possible by following [[Wikipedia:Core content policies|core content policies]]. The Verifiability policy maintains that "all material <em>must</em> be attributable to reliable, published sources." This means, when adding information: you must be able to back up each statement with a source. It must not only be possible to verify a claim, but also [[Wikipedia:Citation underkill#Feasibility and original reporting|feasible]]. This is best achieved by using [[Wikipedia:Inline citations|inline citation]]s, and plenty of them.

One cause for "citation underkill" is the thought that it does not matter when good content is unsourced—or that [[general knowledge]] needs no citations. The line separating {{em|general knowledge}} from [[traditional knowledge|folk knowledge]], [[folk lore|folk belief]], and [[superstition]] is thin. By allowing certain statements to go unreferenced, Wikipedia risks furthering [[false belief]]s and spreading [[Fallacy|errors in reasoning]] and [[List of common misconceptions|widely held misconceptions]].

Without citations, it is difficult to know that material isn't just made up. It is critically important for an article to be verifiable, especially when sources disagree, in order to maintain a [[Wikipedia:Neutral point of view|neutral point of view]]. [[Wikipedia:Citation underkill#Citation balancekill|Changing single words can cause a statement that was sourced]], to become a statement which [[Wikipedia:Verifiability#Tagging a sentence, section, or article|fails verification]]. When no citation is nearby, this [[Wikipedia:The deadline is now|error risks being missed]]. By arguing that a source shouldn't be included, when it can be—we make it hard to verify our articles—putting their neutrality at risk and diminishing their encyclopedic value.

The [[Wikipedia:Citing sources#Text–source integrity|integrity]] of content depends on where a citation is placed. Misplaced citations cause {{em|citation confusion}}, which makes it harder to verify claims. Placing citations where they clearly correspond to specific claims improves the verifiability in accordance with [[Wikipedia:Citing sources#How to place an inline citation using ref tags|guideline on footnotes]]. When no citation is placed to verify a claim or if the citation is a commented out, it decreases the verifiability of content, and readers may incorrectly hold that those statements are unsourced. Unsourced material on Wikipedia risks (rightly or wrongly) being considered as [[Wikipedia:No original research|original research]].

[[Wikipedia:Creating controversial content|Controversial claims]] usually require only single citations, but additional citations may decrease the degree with which the claim is [[Wikipedia:Likely to be challenged|likely to be challenged]]. "[[Wikipedia:Citation overkill|Citation overkill]]" can occur when {{em|many}} (often weak) sources are used to support the same statement, which can give a false sense of authority. Using as many sources as you need to ensure verifiability is not overkill. In most cases, one citation for each statement is sufficient to satisfy verifiability.

== Citations improve article content ==
[[File:Corp2739.jpg|thumb|150px|The color of the sky varies.{{ref|1}}|alt=The color of the sky varies.]]
It is possible that an editor who is trying to promote an article to [[Wikipedia:Good articles|GA-class]] (good article status) might add [[Help:Citation tools|citations]] to basic facts such as "...the sky is blue...".{{ref|3}} This is a [[Wikipedia:The perfect article|good thing]], and the fact that the [[Wikipedia:You do need to cite that the sky is blue|sky is not always blue]] does benefit from adding a citation. We can add citations for things that are [[common knowledge|well-known]], and the source can contain additional information to benefit our readers. For content that [[Wikipedia:Verifiability#Tagging a sentence, section, or article|failed verification]], [[Wikipedia:You do need to cite that the sky is blue|sky blue]] cases are not applicable because the content is not verifiable using the source presented. That means content that failed verification is a violation of [[Wikipedia:Verifiability]] policy. Rather than skim a source and add a point or two, it may have additional information or the same source could be used for a subpage on the same topic. [[Help:How to mine a source]] is a how-to on maximizing the information obtained for a single source. If a claim is only verifiable via [[Wikipedia:Verifiability#Access to sources|WP:PAYWALL]] then it is best to provide a citation. Where you may think citations are not needed they may be needed. For example, [[Wikipedia:Stand-alone lists#Citing sources|stand-alone lists]] such as [[List of electronic cigarette and e-cigarette liquid brands]] are [[Wikipedia:Verifiability#Responsibility for providing citations|required to be sourced]] in the same manner as other articles. Wikipedia has [[Wikipedia:Ignore all rules|no firm rules]], but by following the rules it is very possible to maintain a [[Wikipedia:Competence is required|high quality of article content]].{{ref|4}} For example, see the [[Larry Sanger]] article. If a [[Wikipedia:Policies and guidelines|rule]] prevents you from improving a page, then the rule is [[truth|wrong or you are wrong]]. Think twice before breaking a rule.

=== Citing common knowledge ===
[[File:Korean fans closeup.jpg|thumb|150px|Electric fans in South Korea commonly feature a timer, due to a widely held misconception that leaving them on while asleep can be fatal.{{ref|2}}<br/>If you really can't find a source to cite for your "obvious" statement, is it really [[Wikipedia:But it's true!|true]]?|alt=Electric fans in South Korea commonly feature a timer, due to a widely held misconception that leaving them on while asleep can be fatal. If you really can't find a source to cite for your "obvious" statement, is it really true?]]
One cause for "citation underkill" is the belief that something is such [[common knowledge]] it needs no support. The line separating {{em|common knowledge}} from [[traditional knowledge|folk knowledge]], [[folk lore|folk belief]], and [[superstition]] is thin. By allowing statements of fact or belief to go unreferenced Wikipedia risks furthering [[false belief]]s and spreading [[Fallacy|fallacies]] and [[List of common misconceptions|widely held misconceptions]]. Without a citation, unsupported content may be [[Wikipedia:Editing policy#Try to fix problems|deleted]] because the content may be considered incorrect.

Wikipedia editors can make [[Wikipedia:Competence is required|mistakes]], and assuming what you think is common knowledge may not be accepted as common knowledge by others. Set an example by citing your content properly, whether you think it is common or uncommon.

=== Citations in the lead ===

Adding [[Wikipedia:Manual of Style/Lead section#Citations|citations to the lead]] is done on a case-by-case basis. Providing citations in the lead can be very helpful, both for readers as well as editors. Without citations in the lead, our readers may think the content is not neutral or is original research, even if sourced in the body. We cannot expect our readers to always read the body to try to verify the content they read in the lead. Citations in the lead also help [[Wikipedia:Time management|readers and editors find their way in the body of the article]], when the citation supports the same or similar statements in different parts of the article. Contentious articles or articles on contentious topics benefit especially from citations in the lead.

=== Bundling citations ===

[[Wikipedia:Citing sources#Bundling citations|WP:CITEBUNDLE]] claims bundling citations has several advantages, without explaining in detail when bundling poses disadvantages. When multiple citations are bundled into a single footnote, especially when bundling all the citations at the end of the sentence or paragraph it may be difficult to verify the article content. Another argument against bundling is that it presents an extra step for anyone wanting to review the source for a claim. When different citations support different parts of the same sentence bundling can cause citation confusion. It is best to unbundle bundled citations and place them where they verify each statement when different sources verify different parts of a sentence or paragraph. Ease of verification helps readers and editors.

[[Wikipedia:Verifiability]] states "In Wikipedia, ''verifiability'' means that other people using the encyclopedia can check that the information comes from a [[Wikipedia:Verifiability#What counts as a reliable source|reliable source]]." When different sources verify different parts of a sentence or paragraph, moving all the citations to the end of a sentence or paragraph makes it difficult to check whether each statement is verifiable. Verifiability policy also states "The cited source must clearly support the material as presented in the article. Cite the source clearly and precisely (specifying page, section, or such divisions as may be appropriate)." This means the content must be clearly supported by the cited source. An editor may think the content failed verification if the citations are misplaced.

In certain cases bundling citations may help readability, but if you're only talking about a handful of references—it likely doesn't. Bundling properly can be difficult and time-consuming, if you're not willing to put in the work—you're likely to leave a botched mess. It's better to leave citations visible unless you really know what you're doing.

;Bundling correctly

When the sources verify the exact statement the citations may be bundled this way: The color of the sky changes at the beginning and at the end of the day.<ref>References:
* {{cite book|author=Frank Staub|title=The Kids' Book of Clouds and Sky|url=https://books.google.com/books?id=mxCgo_LViPgC&pg=PA10|year=2005|publisher=Sterling Publishing Company, Inc.|isbn=978-1-4027-2806-8|pages=10–}}
* {{cite book|author=Lucia Ronchi|title=The Semantics of Color Sharing the Laboratory with Color Vision|volume=II|url=https://books.google.com/books?id=ZBRbAwAAQBAJ&pg=PA69|date=1 April 2014|publisher=Fondazione Giorgio Ronchi|isbn=978-88-88649-41-2|pages=69–}}</ref>
{{reflist}}

;Bundling incorrectly

Bundling all the citations at the end of the sentence would make it difficult to verify each specific piece of content when multiple pieces of content require verification from difference sources or when 17 different pieces of content require verification from difference sources such as the following sentence: Aluminum, barium, cadmium, chromium, copper, iron, lead, manganese, mercury, nickel, silicate, silver, strontium, tin, titanium, zinc, and zirconium have been found in the electronic cigarette aerosol.<ref>References:
* {{cite journal|last=Grana|first=R|author2=Benowitz, N|author3=Glantz, SA|title=E-cigarettes: a scientific review.|journal=Circulation|date=13 May 2014|volume=129|issue=19|pages=1972–86|doi=10.1161/circulationaha.114.007667|pmc=4018182|pmid=24821826}}
* {{cite journal|last1=Cheng|first1=T.|title=Chemical evaluation of electronic cigarettes|journal=Tobacco Control|volume=23|issue=Supplement 2|year=2014|pages=ii11–ii17|issn=0964-4563|doi=10.1136/tobaccocontrol-2013-051482|pmc=3995255|pmid=24732157}}
* {{cite journal|last1=Farsalinos|first1=K. E.|last2=Polosa|first2=R.|title=Safety evaluation and risk assessment of electronic cigarettes as tobacco cigarette substitutes: a systematic review|journal=Therapeutic Advances in Drug Safety|volume=5|issue=2|year=2014|pages=67–86|issn=2042-0986|doi=10.1177/2042098614524430|pmc=4110871|pmid=25083263}}
* {{cite journal|last1=Dagaonkar RS|first1=R.S.|last2=Udwadi|first2=Z.F.|title=Water pipes and E-cigarettes: new faces of an ancient enemy|journal=Journal of the Association of Physicians of India|volume=62|issue=4|year=2014|pages=324–328|url=http://www.japi.org/april_2014/05_ra_water_pipes.pdf|pmid=25327035}}
* {{cite journal|last1=Rom|first1=Oren|last2=Pecorelli|first2=Alessandra|last3=Valacchi|first3=Giuseppe|last4=Reznick|first4=Abraham Z.|title=Are E-cigarettes a safe and good alternative to cigarette smoking?|journal=Annals of the New York Academy of Sciences|volume=1340|issue=1|year=2014|pages=65–74|issn=00778923|doi=10.1111/nyas.12609|pmid=25557889}}
* {{cite journal|last1=Farsalinos|first1=Konstantinos|last2=Voudris|first2=Vassilis|last3=Poulas|first3=Konstantinos|title=Are Metals Emitted from Electronic Cigarettes a Reason for Health Concern? A Risk-Assessment Analysis of Currently Available Literature|journal=International Journal of Environmental Research and Public Health|volume=12|issue=5|year=2015|pages=5215–5232|issn=1660-4601|doi=10.3390/ijerph120505215|pmc=4454963|pmid=25988311}}</ref> For this particular case, it easier to verify each piece of content when each citation is placed where it verifies each claim.
{{reflist}}

<blockquote style="background:white; padding:1em; border:1px solid #999;"><!--code for display-->
If the sources verify different parts of the sentence or paragraph then bundling the citations will make it take longer to verify each statement. Therefore, putting all the citations at the end would make it difficult for a reader to know which piece of content comes from which citation. This is done on a case-by-case basis.</blockquote>

=== Hidden citations ===
{{shortcut|WP:VISIBLECITATION}}
If consecutive sentences are supported by the same citation, it is [[Wikipedia:What %22Ignore all rules%22 means#Use common sense|better for them to be all visibly shown]]. Hiding citations with the markup <code><nowiki><!--  --></nowiki></code> makes it difficult for our readers to verify claims. If citations are hidden it often is better to make them visible. References can occur and can become unhidden after each sentence, which is the preferred style for [[Wikipedia:Citations in medical articles|medical content]]. Hiding citations can cause confusion in the future.{{ref|5}} For example, putting only one reference at the end of a section can require ongoing maintenance as other editors may mistakenly add <nowiki>{{cn}}</nowiki> tags or delete content that they believe is unreferenced.

== Necessary repetition ==
{{shortcut|WP:REPEATCITATION}}
To improve verifiability, material that is repeated multiple times throughout an article should have an inline citation for every mention. Doing so also increases the chance readers and editors will find the appropriate source for each statement. Without an inline citation next to each claim, it is difficult for readers to verify claims. Therefore, it is perfectly reasonable to provide inline citations repeatedly. For example: to state that the human hand has four fingers and one thumb{{ref|6}} in multiple places in an article, you would do well to provide a citation after each mention. This can be accomplished by adding to the main citation a markup like this: <code><nowiki></nowiki>{{zwsp}}<nowiki><ref name=Latash2008></nowiki></code>, while using a corresponding named-ref abbreviated citation like this: <code><nowiki></nowiki>{{zwsp}}<nowiki><ref name=Latash2008/></nowiki></code>.

Citation underkill often occurs when:
* Inline citation is provided only at the end of a paragraph
* In certain circumstances, when all sources are placed at the end of a sentence
{{in5}}An example of how to place sources in the middle of a sentence, in an example where it is appropriate:

<blockquote style="background:white; padding:1em; border:1px solid #999;"><!--code for display-->
Tomato products, such as ketchup, tomato juice, spaghetti sauce, and pizza sauce are high in [[lycopene]],<sup class="reference">[1]</sup> which research indicates likely plays a role in protecting against cardiovascular disease and various cancers.<sup class="reference">[2]</sup>

{{refbegin}}
# <ref name=ArabSteck2000>{{cite journal|last1=Arab|first1=Lenore|last2=Steck|first2=Susan|title=Lycopene and cardiovascular disease.|journal=Am J Clin Nutr|year=2000|volume=71|issue=6 Suppl|pages=1691S-5S; discussion 1696S-7S|pmid=10837319|url=http://ajcn.nutrition.org/content/71/6/1691s.long}}</ref>
# <ref name=OmoniAluko2005>{{cite journal|last1=Omoni|first1=Adetayo O.|last2=Aluko|first2=Rotimi E.|title=The anti-carcinogenic and anti-atherogenic effects of lycopene: a review|journal=Trends in Food Science & Technology|volume=16|issue=8|year=2005|pages=344–350|issn=09242244|doi=10.1016/j.tifs.2005.02.002}}</ref>
{{reflist}}
{{refend}}
</blockquote>

Bundling all the citations together in one citation at the end of a sentence or paragraph often make it difficult to determine which citation verifies which claim. An extreme example where specific claims are verified individually is this:

<blockquote style="background:white; padding:1em; border:1px solid #999;"><!--code for display-->
Aluminum,<sup class="reference">[1]</sup> barium,<sup class="reference">[2]</sup> cadmium,<sup class="reference">[3]</sup> chromium,<sup class="reference">[4]</sup> copper,<sup class="reference">[5]</sup> iron,<sup class="reference">[6]</sup> lead,<sup class="reference">[7]</sup> manganese,<sup class="reference">[8]</sup> mercury,<sup class="reference">[9]</sup> nickel,<sup class="reference">[10]</sup> silicate,<sup class="reference">[11]</sup> silver,<sup class="reference">[12]</sup> strontium,<sup class="reference">[13]</sup> tin,<sup class="reference">[14]</sup> titanium,<sup class="reference">[15]</sup> zinc,<sup class="reference">[16]</sup> and zirconium have been found in the electronic cigarette aerosol.<sup class="reference">[17]</sup>

{{refbegin}}
# <ref name=Grana2014>{{cite journal|last=Grana|first=R|author2=Benowitz, N|author3=Glantz, SA|title=E-cigarettes: a scientific review.|journal=Circulation|date=13 May 2014|volume=129|issue=19|pages=1972–86|doi=10.1161/circulationaha.114.007667|pmc=4018182|pmid=24821826}}</ref>
# <ref name=FarsalinosVoudris2015/>
# <ref name=Rom2014/>
# <ref name=Cheng2014>{{cite journal|last1=Cheng|first1=T.|title=Chemical evaluation of electronic cigarettes|journal=Tobacco Control|volume=23|issue=Supplement 2|year=2014|pages=ii11–ii17|issn=0964-4563|doi=10.1136/tobaccocontrol-2013-051482|pmc=3995255|pmid=24732157}}</ref>
# <ref name=FarsalinosPolosa2014>{{cite journal|last1=Farsalinos|first1=K. E.|last2=Polosa|first2=R.|title=Safety evaluation and risk assessment of electronic cigarettes as tobacco cigarette substitutes: a systematic review|journal=Therapeutic Advances in Drug Safety|volume=5|issue=2|year=2014|pages=67–86|issn=2042-0986|doi=10.1177/2042098614524430|pmc=4110871|pmid=25083263}}</ref>
# <ref name=FarsalinosPolosa2014/>
# <ref name=Rom2014/>
# <ref name=FarsalinosVoudris2015/>
# <ref>{{cite journal|last1=Dagaonkar RS|first1=R.S.|last2=Udwadi|first2=Z.F.|title=Water pipes and E-cigarettes: new faces of an ancient enemy|journal=Journal of the Association of Physicians of India|volume=62|issue=4|year=2014|pages=324–328|url=http://www.japi.org/april_2014/05_ra_water_pipes.pdf|pmid=25327035}}</ref>
# <ref name=Rom2014>{{cite journal|last1=Rom|first1=Oren|last2=Pecorelli|first2=Alessandra|last3=Valacchi|first3=Giuseppe|last4=Reznick|first4=Abraham Z.|title=Are E-cigarettes a safe and good alternative to cigarette smoking?|journal=Annals of the New York Academy of Sciences|volume=1340|issue=1|year=2014|pages=65–74|issn=00778923|doi=10.1111/nyas.12609|pmid=25557889}}</ref>
# <ref name=FarsalinosPolosa2014/>
# <ref name=FarsalinosPolosa2014/>
# <ref name=FarsalinosVoudris2015/>
# <ref name=FarsalinosPolosa2014/>
# <ref name=FarsalinosVoudris2015/>
# <ref name=FarsalinosVoudris2015/>
# <ref name=FarsalinosVoudris2015>{{cite journal|last1=Farsalinos|first1=Konstantinos|last2=Voudris|first2=Vassilis|last3=Poulas|first3=Konstantinos|title=Are Metals Emitted from Electronic Cigarettes a Reason for Health Concern? A Risk-Assessment Analysis of Currently Available Literature|journal=International Journal of Environmental Research and Public Health|volume=12|issue=5|year=2015|pages=5215–5232|issn=1660-4601|doi=10.3390/ijerph120505215|pmc=4454963|pmid=25988311}}</ref>
{{reflist}}
{{refend}}
</blockquote>

* This example is extreme, and for certain situations can be rewritten, but to avoid readers or editors needing to scour through different sources—one citation is needed after each statement.

[[Wikipedia:Citation overkill]] suggests that repetitive use of the same inline citations is overkill and causes clutter, but the advantage of doing so helps an editor or reader quickly locate the citation and check to make sure the content is properly [[Wikipedia:No original research|sourced]]. After an editor clicks to edit an article, it often states at the top, "Encyclopedic content must be verifiable." Removing a citation while citing [[Wikipedia:Citation overkill#Needless repetition|WP:REPCITE]], for example, may lead to difficulty in verifying a claim or it may even be perceived as a violation of Wikipedia's [[Wikipedia:Verifiability|Verifiability]] policy. Placing a citation at the end of each paragraph instead of after each sentence within that paragraph may result in the content being tagged with a [[Wikipedia:Citation needed|citation needed]] tag. It is better to place a citation at the end of each sentence to improve the ability to verify each statement. The content could be mistakenly deleted if someone thinks the content is unsourced.

<blockquote style="background:white; padding:1em; border:1px solid #999;"><!--code for display-->
To summarize, do not remove citations simply because they are being repeated. Citing each sentence improves an article's verifiability, which is preferred over paragraph citations. Editors should be cautioned against taking actions that make it harder to verify a specific claim.
</blockquote>

=== Sentence merging ===

Merging a sentence without a citation with a sentence that does have a citation can render the newly formed sentence as partially failed verification. This can occur when a sentence was added into a paragraph without a citation. Merging sentences together without using the appropriate citations cause citation craziness. If you want to delete a sentence then be sure that the citation left behind is not misplaced. If you delete a sentence that verified only that claim then you should also delete the citation that verified that claim. If you leave behind the citation it may not verify the previous statement. If more than one source is being used to verify a claim and you are changing the wording that is verifiable to only one source, then be sure to remove the other sources that do not verify the new claim. When adding wholly new information, make sure it is cited to the correct citation. [[Wikipedia:Don't hijack references|Citation hijacking]] occurs when adding new information before an existing citation where it does not verify the claim. When an editor rewrites a sentence that is properly sourced and adds one or more citations where there already is a citation at the end of a sentence it may cause a problem. The new citation may verify the new sentence but often the original citation used to verify the previous sentence does not verify the new sentence.

== Citation placement ==
{{shortcut|WP:CITATIONPLACEMENT}}
When multiple sources support different parts of a paragraph or passage it is important to place each citation where they verify each specific concept or idea. This also acts to increase the life-span of text on Wikipedia. If you write a paragraph, which later gets a new statement added in the middle of it—citing a different source{{snd}} you will have {{em|citation confusion}}.

Simple claims can become confusing to verify. In certain circumstances, to avoid citation confusion it is easier to verify each specific claim by placing the citation where it verifies each claim, rather than place all the citations at the end of the sentence or paragraph.

A clear example of this can be found at [[Malaria]], where one citation is broken up by another, and where citations at the end of a paragraph makes it more difficult to [[Wikipedia:Verifiability|verify]]:
<blockquote style="background:white; padding:1em; border:1px solid #999;"><!--code for display-->
;Most useful
<span style="background:yellow;>The signs and symptoms of malaria typically begin 8–25 days following infection;</span><ref name=PPID2010/> <span style="background:#eeaeee;">however, symptoms may occur later in those who have taken antimalarial medications as prevention.</span><ref name=Nadjm2012/> <span style="background:#e0ffff;">Initial manifestations of the disease—common to all malaria species—are similar to [[flu]]-like symptoms,</span><ref name=Bartoloni2012/><span style="background:#eeaeee;"> and can resemble other conditions such as [[sepsis]], [[gastroenteritis]], and [[viral disease]]s.</span><ref name=Nadjm2012/><span style="background:#ecf2ea;"> The presentation may include [[headache]], [[fever]], [[shivering]], [[arthralgia|joint pain]], [[vomiting]], [[hemolytic anemia]], [[jaundice]], [[hemoglobinuria|hemoglobin in the urine]], [[Retinopathy|retinal damage]], and [[convulsion]]s.</span><ref name=Beare2006/>
</blockquote>
<blockquote style="background:white; padding:1em; border:1px solid #999;"><!--code for display-->
;Less useful
<span style="background:yellow;>The signs and symptoms of malaria typically begin 8–25 days following infection;</span><ref name=PPID2010/> <span style="background:#eeaeee;">however, symptoms may occur later in those who have taken antimalarial medications as prevention.</span><ref name=Nadjm2012/> <span style="background:#ffA9A9;">Initial manifestations of the disease—common to all malaria species—are similar to [[flu]]-like symptoms, and can resemble other conditions such as [[sepsis]], [[gastroenteritis]], and [[viral disease]]s.</span><ref name=Nadjm2012/><ref name=Bartoloni2012/><span style="background:#ecf2ea;"> The presentation may include [[headache]], [[fever]], [[shivering]], [[arthralgia|joint pain]], [[vomiting]], [[hemolytic anemia]], [[jaundice]], [[hemoglobinuria|hemoglobin in the urine]], [[Retinopathy|retinal damage]], and [[convulsion]]s.</span><ref name=Beare2006/>
</blockquote>
<blockquote style="background:white; padding:1em; border:1px solid #999;"><!--code for display-->
;Least useful (nearly pointless)
<span style="background:#ffA9A9;">The signs and symptoms of malaria typically begin 8–25 days following infection; however, symptoms may occur later in those who have taken antimalarial medications as prevention. Initial manifestations of the disease—common to all malaria species—are similar to [[flu]]-like symptoms, and can resemble other conditions such as [[sepsis]], [[gastroenteritis]], and [[viral disease]]s. The presentation may include [[headache]], [[fever]], [[shivering]], [[arthralgia|joint pain]], [[vomiting]], [[hemolytic anemia]], [[jaundice]], [[hemoglobinuria|hemoglobin in the urine]], [[Retinopathy|retinal damage]], and [[convulsion]]s.</span><ref name=PPID2010/><ref name=Nadjm2012/><ref name=Bartoloni2012/><ref name=Beare2006/>
</blockquote>
<blockquote style="background:white; padding:1em; border:1px solid #999;"><!--code for display-->
;References
{{refbegin}}
<ref name=PPID2010>{{cite book|vauthors=Fairhurst RM, Wellems TE|chapter=Chapter 275. ''Plasmodium'' species (malaria)|veditors=Mandell GL, Bennett JE, Dolin R|title=Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases|volume=2|edition=7th|year=2010|publisher=Churchill Livingstone/Elsevier|location=Philadelphia, Pennsylvania|isbn=978-0-443-06839-3|pages=3437–62}}</ref>
<ref name=Nadjm2012>{{cite journal|vauthors=Nadjm B, Behrens RH|title=Malaria: An update for physicians|journal=Infectious Disease Clinics of North America|year=2012|volume=26|issue=2|pages=243–59|doi=10.1016/j.idc.2012.03.010|pmid=22632637}}</ref>
<ref name=Bartoloni2012>{{cite journal|vauthors=Bartoloni A, Zammarchi L |title=Clinical aspects of uncomplicated and severe malaria|journal=Mediterranean Journal of Hematology and Infectious Diseases|year=2012|volume=4|issue=1|pages=e2012026|doi=10.4084/MJHID.2012.026|pmc=3375727|pmid=22708041}}{{open access}}</ref>
<ref name=Beare2006>{{cite journal|vauthors=Beare NA, Taylor TE, Harding SP, Lewallen S, Molyneux ME |title=Malarial retinopathy: A newly established diagnostic sign in severe malaria|journal=American Journal of Tropical Medicine and Hygiene|year=2006|volume=75|issue=5|pages=790–7|pmc=2367432|pmid=17123967|url=http://www.ajtmh.org/cgi/pmidlookup?view=long&pmid=17123967}} {{open access}}</ref>
{{refend}}
<references/>
</blockquote>

Benefits of proper citation are not limited to [[Wikipedia:Biomedical information|medicine]], and a good example of proper use of citations can be found in the [[Wikipedia:Featured articles|Featured article]] on [[Ukiyo-e]] (exhibited on the main page on 25 June 2017):
<blockquote style="background:white; padding:1em; border:1px solid #999;"><!--code for display-->

Determining at what prices prints sold is a challenge for experts, as records of hard figures are scanty and there was great variety in the production quality, size,{{sfn|Kobayashi|Ōkubo|1994|p=216}} supply and demand,{{sfn|Ōkubo|2013|p=31}} and methods, which went through changes such as the introduction of full-colour printing.{{sfn|Ōkubo|2013|p=32}} How expensive prices can be considered is also difficult to determine as social and economic conditions were in flux throughout the period.{{sfn|Kobayashi|Ōkubo|1994|pp=216—217}}  In the 19th century, records survive of prints selling from as low as 16 ''{{transl|ja|[[Japanese mon (currency)|mon]]}}''{{sfn|Ōkubo|2008|pp=151—153}} to 100 ''{{transl|ja|mon}}'' for deluxe editions.{{sfn|Kobayashi|Ōkubo|1994|p=217}} Jun'ichi Ōkubo suggests that prices in the 20s and 30s of ''{{transl|ja|mon}}'' were likely common for standard prints.{{sfn|Ōkubo|2013|p=43}} As a loose comparison, a bowl of [[soba]] noodles in the early 19th century typically sold for 16 ''mon''.{{sfnm|1a1=Kobayashi|1a2=Ōkubo|1y=1994|1p=217|2a1=Bell|2y=2004|2p=174}}</blockquote>

* {{cite book|last1=Kobayashi|first1=Tadashi|last2=Ōkubo|first2=Jun'ichi|script-title=ja:浮世絵の鑑賞基礎知識|trans-title=Fundamentals of Ukiyo-e Appreciation|publisher=Shibundō|year=1994|language=Japanese|isbn=978-4-7843-0150-8}}
* {{cite book|last=Ōkubo|first=Jun'ichi|script-title=ja:カラー版 浮世絵|trans-title=Ukiyo-e: Colour Edition|year=2008|publisher=Iwanami Shoten|language=Japanese|isbn=978-4-00-431163-8}}
* {{cite book|last=Ōkubo|first=Jun'ichi|script-title=ja:浮世絵出版論|trans-title=On Ukiyo-e Publishing|year=2013|publisher=Fujiwara Printing|language=Japanese|isbn=978-4-642-07915-0}}
* {{cite book|last=Bell|first=David|title=Ukiyo-e Explained|year=2004|publisher=[[Global Oriental]]|isbn=978-1-901903-41-6}}
{{reflist}}

== Citing different page numbers ==

Citing the page number or page numbers for the specific content used to source the statement or quotation in the article, makes it easier to verify the claim rather than a page range using the same repeated citation. If you are citing a book or PDF file then citing the specific page number or page numbers can be especially helpful for anyone reading the source.

One way to verify each specific page number without creating duplicate full citations is like this:

Enhancing the availability of drinking water can lead to clear beneﬁts to health.{{sfn|WHO|2016|p=1}} Drinking water containing nitrate and nitrite has been linked to [[methaemoglobinaemia]], in particular to bottle-fed babies.{{sfn|WHO|2016|p=6}} It is recommended that water be absent of tastes and odors that would be unpleasant to most people.{{sfn|WHO|2016|p=7}}

* {{cite web|url=http://www.who.int/water_sanitation_health/dwq/gdwq0506.pdf|title=Guidelines for Drinking-water Quality|publisher=World Health Organization|year=2006|ref={{harvid|WHO|2016}}}}
{{reflist}}

A <code><nowiki></nowiki>{{zwsp}}<nowiki>== Bibliography ==</nowiki></code> section can be created for adding the main citation and a named-ref abbreviated citation is used for each page number. The named-ref abbreviated citation is placed specifically where it verifies the claim.

The main citation looks like this: <code><nowiki></nowiki>{{zwsp}}<nowiki>{{cite web|url=http://www.who.int/water_sanitation_health/dwq/gdwq0506.pdf|title=Guidelines for Drinking-water Quality|publisher=World Health Organization|year=2006|ref={{harvid|WHO|2016}}}}</nowiki></code> and the named-ref abbreviated citation looks like this: <code><nowiki></nowiki>{{zwsp}}<nowiki>{{sfn|WHO|2016|p=7}}</nowiki></code>.

Another way to provide a page number for each citation is by using the markup <code><nowiki></nowiki>{{zwsp}}<nowiki>{{rp|}}</nowiki></code>. This is accomplished by placing it at end of the citation like this: <ref name=WHO2016>{{cite web|url=http://www.who.int/water_sanitation_health/dwq/gdwq0506.pdf|title=Guidelines for Drinking-water Quality|publisher=World Health Organization|year=2006}}</ref>{{rp|7}}
{{reflist}}

== Citation balancekill ==
{{shortcut|WP:CITEACCURACY}}
[[File:I Am Weasel (15483000477).jpg|thumb|150px|Stating "Some weasels are white." may be engaging in unacceptable [[Wikipedia:No original research|original research]] if the source does not explicitly state that "some" are white.|alt=Stating "Some weasels are white." may be engaging in unacceptable original research if the source does not explicitly state that "some" are white.]]
Placing a citation after each idea or concept does not guarantee the content is verifiable. [[Wikipedia:Consensus|Consensus]] on Wikipedia does not magically generate accuracy. An editor may propose a [[Wikipedia:There are no oracles|change to consensus]] by [[Wikipedia:Consensus#Through discussion|discussion]] or [[Wikipedia:Consensus#Through editing|editing]]. The verifiability of the content depends heavily on whether the content is in actuality verified to the source placed after each idea or concept. Furthermore, placing an inline citation where it verifies the content is important, but it is equally or even more important for the content to be [[Wikipedia:NPOV means neutral editing, not neutral content|neutrally written]]. By following [[Wikipedia:Core content policies|Neutral point of view, Verifiability and No original research policies]], citation balancekill (the sum of accurately sourced knowledge) is attainable. Altering the original meaning of the content may violate [[Wikipedia:Verifiability|verifiable]] policy. The content is more accurate and neutral when including a modifier or [[Wikipedia:Writing better articles#Avoid peacock and weasel terms|weasel word]] supported by the source. Adding a modifier to a sentence not supported by the source alters the original meaning of the source. [[Weasel word]]s or [[Wikipedia:Manual of Style/Words to watch#Unsupported attributions|unsupported attributions]] are words and phrases that give an appearance that something explicate has been stated, when in actuality only a vague or ambiguous claim has been presented.{{ref|7}} When a source only indicates a vague or ambiguous claim then the content added to an article should also indicate a vague or ambiguous claim.

Even changing single words or certain phrases can render content from being sourced, to content that has [[Wikipedia:Verifiability#Tagging a sentence, section, or article|failed verification]]. Even when the content meets verifiability policy an editor may rewrite the content years later. For example, another editor comes along and adds a phrase or makes a modification to a sentence. Now, the new sentence basically says something that the source does not mention; effectively making the once verifiable sentence, a case of failed verification. This issue is often overlooked. If the source expresses a specified viewpoint such as using the word "some" then the content can also specify that viewpoint or similar viewpoint which avoids giving a misleading or vague impression. We can use the exact weasel word or a synonym to that word when the source has used that specific word. We cannot use the word "some" when the source uses another weasel word that does give a different viewpoint such as numerous or substantial. If the source does not use the word "some" or by combining different sources together to come to the conclusion that it is "some", then it probably is original research or a synthesis violation.

<blockquote style="background:white; padding:1em; border:1px solid #999;"><!--code for display-->
Do not combine material from different sources to reach or imply a conclusion not explicitly stated by any given source. This would be improper editorial synthesis to suggest a new conclusion. Combining sources to come to a new conclusion is original research performed by an editor. It is acceptable only when a [[Wikipedia:Identifying reliable sources|reliable source]] has published the same argument in relation to the topic of the article.
</blockquote>

[[Wikipedia:No original research]] (in particular, [[Wikipedia:No original research#Synthesis of published material|Synthesis of published material]]) clearly indicates we don't conduct our own reviews of the sources on Wikipedia.{{ref|8}} For example, when two reviews verify the same content we can't state "Two reviews found...". This would in effect be combining material from different sources to reach a conclusion not explicitly stated in any individual source. The content must be able to be verifiable to a reliable source, not by counting of references that are present in a Wikipedia article.{{ref|9}} It is not an allowable provision to include content that failed verification. Therefore, we can't state "Two reviews found..." unless an individual source stated it was "Two reviews...". Moreover, when there is no serious dispute between sources, the content should [[Wikipedia:Neutral point of view/FAQ#Assert facts.2C not opinions|normally be asserted]] [[Wikipedia:Citing sources#In-text attribution|without in-text attribution]].

For example, "There is some evidence that following this diet may lead to improvements in terms of body composition and metabolic effects compared with the typical [[Western diet]].[3]"{{ref|10}} This is incorrect. The part "some" has failed verification. The word some is an unsupported weasel word because the source does not explicitly use the word some to support that word in reference to that content. See [[Wikipedia:Manual of Style/Words to watch#Unsupported attributions|WP:SOME]]. The guideline shortcut for the unsupported weasel word some is <code><nowiki></nowiki>{{zwsp}}<nowiki>WP:SOME</nowiki></code>. The following is correct: The evidence indicates that following this diet may lead to improvements in terms of body composition and metabolic effects compared with the typical [[Western diet]].<ref name=Katz2014>{{cite journal|last1=Katz|first1=D.L.|last2=Meller|first2=S.|title=Can We Say What Diet Is Best for Health?|journal=Annual Review of Public Health|volume=35|issue=1|year=2014|pages=83–103|issn=0163-7525|doi=10.1146/annurev-publhealth-032013-182351|pmid=24641555|url=http://www.annualreviews.org/doi/full/10.1146/annurev-publhealth-032013-182351}}</ref>
{{reflist}}

Another example is the following: E-cigarettes are likely safer than [[tobacco]].<ref name=KnorstBenedetto2014/> This is incorrect. The part "likely" has failed verification. The following is correct: E-cigarettes are generally considered safer than [[tobacco]].<ref name=KnorstBenedetto2014>{{cite journal|last1=Knorst|first1=Marli Maria|last2=Benedetto|first2=Igor Gorski|last3=Hoffmeister|first3=Mariana Costa|last4=Gazzana|first4=Marcelo Basso|title=The electronic cigarette: the new cigarette of the 21st century?|journal=Jornal Brasileiro de Pneumologia|volume=40|issue=5|year=2014|pages=564–572|issn=1806-3713|doi=10.1590/S1806-37132014000500013|pmc=4263338|pmid=25410845}}</ref>
{{reflist}}

Editors mistakenly use unsupported weasel words even when they believe they are correct. For example, as of 18:05, 28 June 2017‎ Wikipedia's [[Electrical disruptions caused by squirrels]] states: "In the U.S., squirrels have been the cause of many power outages in Pennsylvania.[n 1]"{{ref|11}} This is incorrect. The word "many" has failed verification. Adding up different sources together to come to a new conclusion is a [[Wikipedia:No original research#Synthesis of published material|novel synthesis]]. Another example is the following: "Some have described the Mannings as football's "royal family".[302][303][304][305][306]"{{ref|12}} The word "some" has failed verification. Again, an individual source must make the claim. We don't tell readers what to think. Combining multiples sources to reach a new conclusion does not make it true. When multiple sources say the same thing it does not equate to "some". Even if you believe it to be true, it still must be verifiable.

Bear in mind that we are required to avoid [[Wikipedia:Copyrights|copyright infringement]] and [[Wikipedia:Plagiarism|plagiarism]]. This requires us to [[Wikipedia:Close paraphrasing#When there are a limited number of ways to say the same thing|use our own words]] to express the information we get from the reference. This means we paraphrase and thus words not found in the sources can be used even if they are not the exact same meaning. Changing the wording and rearranging ideas is also an important part of paraphrasing. The information should also be delicately summarized or rephrased [[Wikipedia:No original research#Using sources|without altering its meaning or implication]]. It is possible to construct an alternative wordings without violating the principle of verifiability.

== Overciting content ==
{{shortcut|WP:CITATIONBLOAT}}
[[File:Kitchen-Scissors.jpg|thumb|150px|Removing excessive citations is a reasonable option.|alt=Removing excessive citations is a reasonable option.]]
Quality of citations, not their sheer quantity, improves article content. [[Wikipedia:Reliable sources|Unreliable sources]] can be removed, but it is better if possible to replace them with reliable ones in order to preserve article content. Multiple low quality citations following a statement does not make it more true. Over-citing content especially for non-controversial claims should be avoided.

Editors have cited Citation overkill as a reason for adding additional citations after each sentence for non-controversial claims. Citation overkill appears to support adding more than one citation after each sentence, regardless of circumstance. Editors have misinterpreted Citation overkill into thinking that it is okay to add more than one citation after each claim in any circumstance. This sort of "reference spamming" disrupts the flow of reading an article. Citation overkill states "If there is a good reason to keep multiple citations, for example, to avoid perennial edit warring or because the sources offer a range of beneficial information, clutter may be avoided by merging the citations into a single footnote." If the sources actually do contain beneficial information they could be used to cite other information instead of cluttering the article. If an editor insists on keeping the additional citations they can be commented out using the markup <code><nowiki><!--  --></nowiki></code> in order to avoid cluttering the article with needless citations. On the other hand, merging citations into a single footnote can also clutter the reference section.

Another type of reference spamming is called failed verification spamming. One way to spot failed verification spamming is when an editor who restores the additional citations refuses to provide verification on the talk page for the additional citations. Wikipedia requires that a citation presented for a claim verify the entire claim.{{ref|13}} If the additional citations only partially verifies the claim then the additional citations still failed to verify the claim. It is not a valid argument to keep the additional citations when they do not verify the entire claim. However, if a sentence is making two separate claims it would be best to use a satisfactory source for each, placed following its respective claim. If one of the citations verifies the entire claim then you may only need to use one citation.

One citation after each sentence for non-controversial claims is usually sufficient. Adding more citations than needed can cause {{em|citation bloat}}. More than three citations for non-controversial claims or even controversial claims may be excessive. Reference spamming occurs when an editor adds the same citation multiple places in an article where it is unnecessary or does not verify the claim. Moreover, failed verification spamming occurs when more than one citation is used to try to convince others the claim is sourced when the sources presented does not verify the claim. For [[Wikipedia:Creating controversial content|controversial claims]] one citation is usually enough for content that is [[Wikipedia:Likely to be challenged|likely to be challenged]]. If the claim is extraordinarily controversial then the content may require more than one citation. Adding more than one citation after each statement is done on a case-by-case basis. The purpose of a citation is for readers to be able to verify the content presented, not to persuade to other editors the validity of the content.

In certain circumstances, a very [[Wikipedia:Creating controversial content|controversial claim]] [[Wikipedia:Likely to be challenged|likely to be challenged]] may retain as many as three references, cited in this form:

The benefits and the [[safety of electronic cigarettes|health risks of e-cigarettes]] are uncertain.<ref name=EbbertAgunwamba2015>{{cite journal|last1=Ebbert|first1=Jon O.|last2=Agunwamba|first2=Amenah A.|last3=Rutten|first3=Lila J.|title=Counseling Patients on the Use of Electronic Cigarettes|journal=Mayo Clinic Proceedings|volume=90|issue=1|year=2015|pages=128–134|issn=00256196|doi=10.1016/j.mayocp.2014.11.004|pmid=25572196}}</ref><ref name=Siu2015>{{cite journal|last1=Siu|first1=AL|title=Behavioral and Pharmacotherapy Interventions for Tobacco Smoking Cessation in Adults, Including Pregnant Women: U.S. Preventive Services Task Force Recommendation Statement.|journal=Annals of Internal Medicine|date=22 September 2015|volume=163|pages=622–34|doi=10.7326/M15-2023|pmid=26389730}}</ref><ref name=Harrell2014>{{cite journal|last1=Harrell |first1=PT|last2=Simmons|first2=VN|last3=Correa|first3=JB|last4=Padhya|first4=TA|last5=Brandon|first5=TH|title=Electronic Nicotine Delivery Systems ("E-cigarettes"): Review of Safety and Smoking Cessation Efficacy.|journal=Otolaryngology—head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery|date=4 June 2014|volume=151|pages=381–393|doi=10.1177/0194599814536847|pmc=4376316|pmid=24898072}}</ref>
{{reflist}}

== Feasibility and original reporting ==
[[File:Interior_view_of_Stockholm_Public_Library.jpg|thumb|275px|You don't need to cite the entire library to back up an idea or a concept, but it is better to [[Wikipedia:Citing sources|cite]] something than nothing. Your goal is to strive to cite the {{em|best possible source}}, and to cite in the {{em|best possible way}}.|alt=You don't need to cite the entire library to back up an idea or a concept, but it is better to cite something than nothing. Your goal is to strive to cite the best possible source, and to cite in the best possible way.]]

Verification must be feasible. This {{em|means}}:
* A statement must be able to be verifiable and not constitute [[Wikipedia:No original research|original research]].<br/>For example, not "You can verify this by walking around outside", or "I was listening to an interview". These by definition are original reporting.
* The source must be identifiable.<br/>You can't source "that big book with the blue cover I have in the bookshelf in the downstairs bedroom"—while theoretically verifiable (by one editor), it is in reality not at all verifiable by readers.
* Every statement must have its own verifiable reference following its claim.<br/>
* It must be possible to figure out which source supports which statement.<br/>It is unreasonable to expect an editor or reader to go through dozens of sources in order to find out if the statement is supported by one of them.

This does {{em|not mean}}:
* That the source must be available online;
* That it must be free;
* That it must be or remain in publication; or
* That it must include a [[Wikipedia:Digital Object Identifier|DOI]] or [[Wikipedia:ISBN|ISBN]] (though please do when possible).

== Templates ==

* [[Template:Citation needed]]
* [[Template:Citation needed span]]
* [[Template:Clarify]]
* [[Template:Clarify span]]
* [[Template:Duplication span]]
* [[Template:Excessive citations inline]]
* [[Template:Failed verification]]
* [[Template:Failed verification span]]
* [[Template:Synthesis inline]]
* [[Template:Synthesis inline span]]
* [[Template:Weasel inline]]
* [[Template:Weasel word some span]]
* {{tlx|Welcome-citation}} → regular welcome that encourages citing sources

== Gallery ==
{{Further|Wikipedia:Research help/Videos|Wikipedia:Quick tutorial}}
<gallery caption="Instructional videos on using Wikipedia" widths=165 heights=175 class=center>
File:Wikipedia video tutorial-2-Reliability-en.ogv|alt=Wikipedia video tutorial on reliability.|Wikipedia video tutorial on reliability.
File:Wikipedia guidelines and policies.webm|alt=Wikipedia guidelines and policies.|Wikipedia guidelines and policies.
File:New medical editor.ogv|alt=Guidance for a new medical editor.|Guidance for a new medical editor.
</gallery>

== Userbox ==
{{usbktop}}
{{usbk|User:UserBox/NOTBLUE}}
{{usbkbottom}}

== See also ==
* [[Wikipedia:Avoiding bias]] – an essay showing how to counter bias
* [[Wikipedia:Citation overkill]] – an essay with an opposing viewpoint
* [[Wikipedia:Why most sentences should be cited]]
* {{section link|User:QuackGuru/Reform of Wikipedia|Citation placement}}

== References ==
* {{note|1}}{{cite book|last=Luckiesh|first=Matthew|title=The book of the sky: a résumé of personal experience and observation|url=https://books.google.com/books?id=-4BZAAAAYAAJ&pg=PA90|year=1922|publisher=[[E. P. Dutton]]|pages=90–}}
* {{note|2}}{{cite web|url=http://www.esquire.com/news-politics/q-and-a/a5522/korean-fan-death-0209/|title=Why Do Koreans Think Electric Fans Will Kill Them?|last=Fella|first=Answer|work=[[Esquire (magazine)|Esquire]]|date=22 January 2009}}
* {{note|3}}{{cite book|last=F. Bohren|first=Craig|title=Clouds in a Glass of Beer: Simple Experiments in Atmospheric Physics|url=https://books.google.com/books?id=JLjDAgAAQBAJ&pg=PA96|date=9 April 2013|publisher=[[Courier Corporation]]|isbn=978-0-486-32029-8|pages=96–}}
* {{note|4}}{{cite news|url=http://historynewsnetwork.org/article/125437|title=Wikipedia—The Dumbing Down of World Knowledge|last=Black|first=Edwin|publisher=[[History News Network]]|date=19 April 2010}}
* {{note|5}}{{cite web|url=https://en.wikipedia.org/w/index.php?title=Stevens%E2%80%93Johnson_syndrome&diff=next&oldid=777434169|title=Stevens–Johnson syndrome|publisher=[[Wikipedia]]|date=6 May 2017|author=82.132.226.121}}
* {{note|6}}{{cite book|last=L. Latash|first=Mark|title=Synergy|url=https://books.google.com/books?id=640UDAAAQBAJ&pg=PA137|date=18 March 2008|publisher=[[Oxford University Press, USA]]|isbn=978-0-19-533316-9|pages=137–}}
* {{note|7}}{{cite web|last1=Ganter|first1=Viola|last2=Strube|first2=Michael|title=Finding Hedges by Chasing Weasels: Hedge Detection Using Wikipedia Tags and Shallow Linguistic Features|publisher=[[AFNLP]]|pages=173–176|url=http://www.aclweb.org/anthology/P09-2044|date=4 August 2009}}
* {{note|8}}{{cite web|url=https://en.wikipedia.org/w/index.php?title=Wikipedia:No_original_research&oldid=789151156|title=Wikipedia:No original research|publisher=Wikipedia|date=5 July 2017|author=Wikipedians|quote=<small>Wikipedia does [[Wikipedia:What Wikipedia is not|not]] publish original thought: all material in Wikipedia must be [[Wikipedia:Verifiability|attributable]] to a reliable, published source. Articles may not contain any new analysis or synthesis of published material that serves to reach or imply a conclusion not clearly stated by the sources themselves.</small>}}
* {{note|9}}{{cite web|url=https://en.wikipedia.org/w/index.php?title=Wikipedia:Verifiability&oldid=788671229|title=Wikipedia:Verifiability|publisher=Wikipedia|date=2 July 2017|author=Wikipedians|quote=<small>In Wikipedia, ''verifiability'' means that other people using the encyclopedia can check that the information comes from a [[Wikipedia:Verifiability#What counts as a reliable source|reliable source]]. Wikipedia does not publish [[Wikipedia:No original research|original research]]. Its content is determined by previously published information rather than the beliefs or experiences of its editors.</small>}}
* {{note|10}}{{cite web|url=https://en.wikipedia.org/w/index.php?title=Paleolithic_diet&oldid=790842648#cite_ref-Katz2014_3-1|title=Paleolithic diet|publisher=Wikipedia|date=16 July 2017|author=Wikipedians}}
* {{note|11}}{{cite web|url=https://en.wikipedia.org/w/index.php?title=Electrical_disruptions_caused_by_squirrels&oldid=787972028#cite_ref-Pennsylvania_41-0|title=Electrical disruptions caused by squirrels|publisher=Wikipedia|date=28 June 2017|author=Wikipedians}}
* {{note|12}}{{cite web|url=https://en.wikipedia.org/w/index.php?title=Peyton_Manning&oldid=783491697#cite_ref-302|title=Peyton Manning|publisher=Wikipedia|date=2 June 2017|author=Wikipedians}}
* {{note|13}}{{cite web|url=https://en.wikipedia.org/w/index.php?title=Wikipedia:Verifiability&oldid=854198815|title=Wikipedia:Verifiability|publisher=Wikipedia|date=9 August 2018|author=Wikipedians|quote=<small>All content must be verifiable.</small>}}

{{Wikipedia essays|state=expanded|state1=expanded|state2=expanded|state3=expanded|state4=expanded|state5=expanded}}

[[Category:Wikipedia essays about verification]]
[[Category:Wikipedia essays about building the encyclopedia]]
[[Category:Wikipedia essays about competence]]