"Citation needed" is a tag added by Wikipedia editors to unsourced statements in articles requesting citations to be added. The phrase is reflective of the policies of verifiability and no original research in Wikipedia and has become a general Internet meme. In Wikipedia, the display effect looks like this: 
Usage in Wikipedia
By Wikipedia policy, editors should add citations for content, to ensure accuracy and neutrality, and to avoid original research. In June 2005, Chris Sherlock, a Wikipedia editor with the username Ta bu shi da yu, created the "citation needed" template, to be added to statements without a citation that needed verification. The template is used frequently—397,283 articles in the English Wikipedia are marked with the template.
Usage outside Wikipedia
In 2007, the webcomic xkcd published a comic called "Wikipedian Protester". In the comic, a group of people are listening to a politician's speech, and a protester raises a placard which says "", in Wikipedia's characteristic blue color for internal hyperlinks. This is the first known use of the term outside Wikipedia.[dubious ] This also spawned a meme, on the "explain xkcd" wiki, of placing a "citation needed" tag after obvious statements. Randall Munroe, the creator of xkcd, has also used "" in similar fashion throughout his blog What If?, and, consequently, in the book published as a compilation of the blog's entries.
In 2008, Matt Mechtley created stickers with "", encouraging people to stick them on advertisements. This kind of graffiti has been dubbed "wikiffiti". Quickly becoming an Internet meme, "" appeared not only on billboards, but also some internet kuso pictures. For example, a photograph of George W. Bush's Mission Accomplished speech was doctored so that a "" label was seen under the "mission accomplished" banner.
In 2010, American television hosts Jon Stewart and Stephen Colbert led the Rally to Restore Sanity and/or Fear at the National Mall in Washington, D.C. Some "protesters" held placards with "".
In 2011, German defence minister Karl-Theodor zu Guttenberg was facing accusations that he plagiarized his doctoral thesis. Protesters with "" placards called attention to the many contexts in his thesis where his sources were not labeled.
In 2017, the hosts of the Cognitive Dissonance podcast and the hosts of The Scathing Atheist podcast began working on a weekly podcast with the name Citation Needed. In the podcast, one of the cast is assigned to read an article on Wikipedia and prepares a comedic essay summarizing the article.
- knowyourmeme contributors. "". Know Your Meme. Archived from the original on 2018-06-18. Retrieved 2018-07-27.
- 栗岡 幹英 [Masahide Kurioka] (2010-03-01). "インターネットは言論の公共圏たりうるか：ブログとウィキペディアの内容分析" [The Internet is a Public Sphere of Speech: Content Analysis of Blogs and Wikipedia]. 奈良女子大学社会学論集 [Nara Women's University Sociological Studies] (in Japanese). 奈良女子大学社会学研究会 [Nara Women's University Sociological Study Group] (17): 133–151. ISSN 1340-4032.
- Chris Sherlock. "User Chris Sherlock". Stack Overflow. Archived from the original on 2018-05-10. Retrieved 2018-07-27.
- circular reference] [
- Explainxkcd contributors. "285: Wikipedian Protester – explain xkcd". www.explainxkcd.com. Archived from the original on 2017-10-10. Retrieved 2018-07-27.
- Wikipedia: the missing manual By John Broughton, 2008, ISBN 0-596-51516-2, p. 75 Archived 2018-02-07 at the Wayback Machine
- Munroe, Randall (May 28, 2013). "Alien Astronomers". What If?. Retrieved April 13, 2019.
The Sun is really bright  and its light illuminates the Earth.[note 1]
- Munroe, Randall (2014). "Alien Astronomers". What If?: Serious Scientific Answers to Absurd Hypothetical Questions. New York: Houghton Mifflin Harcourt. p. 128. ISBN 978-0-544-27299-6.
The Sun is really bright, and its light illuminates the Earth.
- Joshua Glenn (2008-01-02). "". Boston.com. Archived from the original on 2018-07-27. Retrieved 2018-07-27.
- "Wikiffiti – stickers that read ". boingboing.net. Archived from the original on 2017-01-14. Retrieved 2018-07-27.
- "[Image – 40120] | ". Know Your Meme. Archived from the original on 2016-03-26. Retrieved 2018-07-27.
- Ted Johnson (2010-11-01). "Satirical rally calls for sanity and/or fear". Variety. Archived from the original on 2010-11-16. Retrieved 2018-07-27.
- Natalia Dannenberg (26 February 2011). "Academics attack German minister in plagiarism row". Deutsche Welle. Archived from the original on 2018-07-27. Retrieved 2018-07-27.
- "Citation Needed, from the Technical Difficulties". IMDb. Retrieved 27 June 2019.
- "About Us". Citation Needed [the podcast]. 2020. Archived from the original on 2020-01-08. Retrieved 2020-01-23.