Wikipedia:Identifying reliable sources
|This page documents an English Wikipedia content guideline. It is a generally accepted standard that editors should attempt to follow, though it is best treated with common sense, and occasional exceptions may apply. Any substantive edit to this page should reflect consensus. When in doubt, discuss first on the talk page.|
|This page in a nutshell: This guideline discusses how to identify reliable sources. The policy on sourcing is Wikipedia:Verifiability. This requires inline citations for any material challenged or likely to be challenged, and for all quotations.|
- To obtain or provide community input on whether a source meets our reliability standards for a particular use, see the reliable sources noticeboard.
Wikipedia articles should be based on reliable, published sources, making sure that all majority and significant minority views that have appeared in those sources are covered (see Wikipedia:Neutral point of view).
The word "source" as used on Wikipedia has three related meanings:
Any of the three can affect reliability. Reliable sources may be published materials with a reliable publication process, authors who are regarded as authoritative in relation to the subject, or both. These qualifications should be demonstrable to other people.
The reliability of a source depends on context. Each source must be carefully weighed to judge whether it is reliable for the statement being made and is an appropriate source for that content. In general, the more people engaged in checking facts, analyzing legal issues, and scrutinizing the writing, the more reliable the publication. Sources should directly support the information as it is presented in an article. If no reliable sources can be found on a topic, Wikipedia should not have an article on it.
The guideline in this page discusses the reliability of various types of sources. The policy on sourcing is Wikipedia:Verifiability, which requires inline citations for any material challenged or likely to be challenged, and for all quotations. The policy is strictly applied to all material in the mainspace—articles, lists, and sections of articles—without exception, and in particular to biographies of living persons, which states:
Contentious material about living persons (or recently deceased) that is unsourced or poorly sourced—whether the material is negative, positive, neutral, or just questionable—should be removed immediately and without waiting for discussion.
In the event of a contradiction between this page and our policies regarding sourcing and attribution, the policy takes priority and editors should seek to resolve the discrepancy. Other policies relevant to sourcing are Wikipedia:No original research and Wikipedia:Biographies of living persons. For questions about the reliability of particular sources, see Wikipedia:Reliable sources/Noticeboard.
Articles should be based on reliable, third-party, published sources with a reputation for fact-checking and accuracy. This means that we only publish the opinions of reliable authors, and not the opinions of Wikipedians who have read and interpreted primary source material for themselves. The following examples cover only some of the possible types of reliable sources and source reliability issues, and are not intended to be exhaustive. Proper sourcing always depends on context; common sense and editorial judgment are an indispensable part of the process.
The term "published" is most commonly associated with text materials, either in traditional printed format or online. However, audio, video, and multimedia materials that have been recorded then broadcast, distributed, or archived by a reputable party may also meet the necessary criteria to be considered reliable sources. Like text sources, media sources must be produced by a reliable third party and be properly cited. Additionally, an archived copy of the media must exist. It is convenient, but by no means necessary, for the archived copy to be accessible via the Internet.
Some types of sources
Many Wikipedia articles rely on scholarly material. When available, academic and peer-reviewed publications, scholarly monographs, and textbooks are usually the most reliable sources. However, some scholarly material may be outdated, in competition with alternative theories, or controversial within the relevant field. Try to cite present scholarly consensus when available, recognizing that this is often absent. Reliable non-academic sources may also be used in articles about scholarly issues, particularly material from high-quality mainstream publications. Deciding which sources are appropriate depends on context. Material should be attributed in-text where sources disagree.
- Articles should rely on secondary sources whenever possible. For example, a review article, monograph, or textbook is better than a primary research paper. When relying on primary sources, extreme caution is advised: Wikipedians should never interpret the content of primary sources for themselves. See Wikipedia:No original research.
- Material such as an article, book, monograph, or research paper that has been vetted by the scholarly community is regarded as reliable. If the material has been published in reputable peer-reviewed sources or by well-regarded academic presses, generally it has been vetted by one or more other scholars.
- Completed dissertations written as part of the requirements for a PhD, and which are publicly available, are considered publications by scholars and can be cited in footnotes if it is shown that they have entered mainstream academic discourse and therefore have been vetted by the scholarly community. This can be done by checking the scholarly citations it has received in citation indices. A corollary is that journals not included in a citation index, especially in fields well covered by such indices, should be used only with caution, and only when other criteria, for example the reputation of the scholar, support their use. Dissertations in progress have not been vetted and are not regarded as published and are thus not reliable sources as a rule. Masters dissertations and theses are only considered reliable if they can be shown to have had significant scholarly influence.
- Isolated studies are usually considered tentative and may change in the light of further academic research. The reliability of a single study depends on the field. Studies relating to complex and abstruse fields, such as medicine, are less definitive. Avoid undue weight when using single studies in such fields. Meta-analyses, textbooks, and scholarly review articles are preferred when available, so as to provide proper context.
- Care should be taken with journals that exist mainly to promote a particular point of view. A claim of peer review is not an indication that the journal is respected, or that any meaningful peer review occurs. Journals that are not peer reviewed by the wider academic community should not be considered reliable, except to show the views of the groups represented by those journals.
News sources often contain both factual content and opinion content. "News reporting" from well-established news outlets is generally considered to be reliable for statements of fact (though even the most reputable reporting sometimes contains errors). News reporting from less-established outlets is generally considered less reliable for statements of fact. Editorial commentary, analysis and opinion pieces, whether written by the editors of the publication (editorials) or outside authors (op-eds) are reliable primary sources for statements attributed to that editor or author, but are rarely reliable for statements of fact.
- When taking information from opinion content, the identity of the author may help determine reliability. The opinions of specialists and recognized experts are more likely to be reliable and to reflect a significant viewpoint. If the statement is not authoritative, attribute the opinion to the author in the text of the article and do not represent it as fact. Reviews for books, movies, art, etc. can be opinion, summary or scholarly pieces.
- For information about academic topics, scholarly sources and high-quality non-scholarly sources are generally better than news reports. News reports may be acceptable depending on the context. Articles which deal in depth with specific studies, as a specialized article on science, are apt to be of more value than general articles which only tangentially deal with a topic. Frequently, although not always, such articles are written by specialist writers who may be cited by name.
- The reporting of rumors has a limited encyclopedic value, although in some instances verifiable information about rumors may be appropriate. Wikipedia is not the place for passing along gossip and rumors.
- Some news organizations have used Wikipedia articles as a source for their work. Editors should therefore beware of circular sourcing.
- Whether a specific news story is reliable for a specific fact or statement in a Wikipedia article will be assessed on a case-by-case basis.
- Some stories are republished or passed along by multiple news organizations. This is especially true for wire services such as the Associated Press. Each single story must only count as being one source.
- News organizations are not required to publish their editorial policy or editorial board online. Many major newspapers do not publish their editorial policies.
- One signal that a news organization engages in fact-checking and has a reputation for accuracy is the publication of corrections.
Self-published and questionable sources
Questionable sources are those with a poor reputation for checking the facts, or with no editorial oversight. Such sources include websites and publications expressing views that are widely acknowledged as extremist, or promotional in nature, or which rely heavily on rumors and personal opinions. Questionable sources are generally unsuitable for citing contentious claims about third parties, which includes claims against institutions, persons living or dead, as well as more ill-defined entities. The proper uses of a questionable source are very limited.
Self-published sources (online and paper)
Anyone can create a personal web page or publish their own book, and also claim to be an expert in a certain field. For that reason self-published media—whether books, newsletters, personal websites, open wikis, blogs, personal pages on social networking sites, Internet forum postings, or tweets—are largely not acceptable. This includes any website whose content is largely user-generated, including the Internet Movie Database (IMDB), CBDB.com, collaboratively created websites such as wikis, and so forth, with the exception of material on such sites that is labeled as originating from credentialed members of the sites' editorial staff, rather than users.
"Blogs" in this context refers to personal and group blogs. Some news outlets host interactive columns they call blogs, and these may be acceptable as sources so long as the writers are professional journalists or are professionals in the field on which they write and the blog is subject to the news outlet's full editorial control. Posts left by readers may never be used as sources; see WP:NEWSBLOG.
Self-published material may sometimes be acceptable when its author is an established expert whose work in the relevant field has been published by reliable third-party publications. Self-published information should never be used as a source about a living person, even if the author is a well-known professional researcher or writer; see WP:BLP#Reliable sources.
Self-published and questionable sources as sources on themselves
Self-published or questionable sources may be used as sources of information about themselves, especially in articles about themselves, without the requirement that they be published experts in the field, so long as:
- the material is neither unduly self-serving nor an exceptional claim;
- it does not involve claims about third parties (such as people, organizations, or other entities);
- it does not involve claims about events not directly related to the subject;
- there is no reasonable doubt as to its authenticity;
- the article is not based primarily on such sources.
Biased or opinionated sources
Wikipedia articles are required to present a neutral point of view. However, reliable sources are not required to be neutral, unbiased, or objective. Common sources of bias include political, financial, religious, philosophical, or other beliefs.
Sometimes "non-neutral" sources are the best possible sources for supporting information about the different viewpoints held on a subject. When dealing with a potentially biased source, editors should consider whether the source meets the normal requirements for reliable sources, such as editorial control and a reputation for fact-checking. Editors should also consider whether the bias makes it appropriate to use in-text attribution to the source, as in "According to the opinion columnist Maureen Dowd..." or "According to the opera critic Tom Sutcliffe..."
Reliability in specific contexts
Biographies of living persons
Editors must take particular care when writing biographical material about living persons. Remove unsourced or poorly sourced contentious material immediately if it is about a living person, and do not move it to the talk page. This applies to any material related to living persons on any page in any namespace, not just article space.
Primary, secondary, and tertiary sources
Wikipedia articles should be based mainly on reliable secondary sources.
Tertiary sources such as compendia, encyclopedias, textbooks, obituaries, and other summarizing sources may be used to give overviews or summaries, but should not be used in place of secondary sources for detailed discussion. Although Wikipedia articles are tertiary sources, Wikipedia employs no systematic mechanism for fact checking or accuracy. Because Wikipedia forbids original research, there is nothing reliable in it that isn't citable with something else. Thus Wikipedia articles (or Wikipedia mirrors) are not reliable sources for any purpose.
Primary sources are often difficult to use appropriately. While they can be both reliable and useful in certain situations, they must be used with caution in order to avoid original research. While specific facts may be taken from primary sources, secondary sources that present the same material are preferred. Large blocks of material based purely on primary sources should be avoided. All interpretive claims, analyses, or synthetic claims about primary sources must be referenced to a secondary source, rather than original analysis of the primary-source material by Wikipedia editors.
Ideal sources for biomedical assertions include general or systematic reviews in reliable, third-party, published sources, such as reputable medical journals, widely recognised standard textbooks written by experts in a field, or medical guidelines and position statements from nationally or internationally reputable expert bodies. Being a "medical source" is not an intrinsic property of the source itself; a source becomes a medical source only when it is used to support a medical claim.
The accuracy of quoted material is paramount and the accuracy of quotations from living persons is especially sensitive. To ensure accuracy, the text of quoted material is best taken from (and cited to) the original source being quoted. If this is not possible, then the text may be taken from a reliable secondary source (ideally one that includes a citation to the original). No matter where you take the quoted text from, it is important to make clear the actual source of the text, as it appears in the article.
Partisan secondary sources should be viewed with suspicion as they may misquote or quote out of context. In such cases, look for neutral corroboration from another source.
Any analysis or interpretation of the quoted material, however, should rely on a secondary source (See: WP:No original research)
The statement that all or most scientists or scholars hold a certain view requires reliable sourcing that directly says that all or most scientists or scholars hold that view. Otherwise, individual opinions should be identified as those of particular, named sources. Editors should avoid original research especially with regard to making blanket statements based on novel syntheses of disparate material. Stated simply, any statement in Wikipedia that academic consensus exists on a topic must be sourced rather than being based on the opinion or assessment of editors.
Usage by other sources
How accepted, high-quality reliable sources use a given source provides evidence, positive or negative, for its reliability and reputation. The more widespread and consistent this use is, the stronger the evidence. For example, widespread citation without comment for facts is evidence of a source's reputation and reliability for similar facts, while widespread doubts about reliability weigh against it. If outside citation is the main indicator of reliability, particular care should be taken to adhere to other guidelines and policies, and to not represent unduly contentious or minority claims. The goal is to reflect established views of sources as far as we can determine them.
Statements of opinion
Some sources may be considered reliable for statements as to their author's opinion, but not for statements asserted as fact without an inline qualifier like "(Author) says...". A prime example of this are opinion pieces in mainstream newspapers. When using them, it is better to explicitly attribute such material in the text to the author to make it clear to the reader that they are reading an opinion.
Note that otherwise reliable news sources—for example, the website of a major news organization—that publish in a "blog" style format for some or all of their content may be as reliable as if published in a more "traditional" 20th-century format.
There is an important exception to sourcing statements of fact or opinion: Never use self-published books, zines, websites, webforums, blogs and tweets as a source for material about a living person, unless written or published by the subject of the biographical material. "Self-published blogs" in this context refers to personal and group blogs; see WP:BLP#Reliable sources and WP:BLP#Using the subject as a self-published source.
- Policies and guidelines
- Wikipedia:Citing sources
- Wikipedia:Identifying reliable sources (medicine)
- Wikipedia:Fringe theories
- Wikipedia:No original research
- Wikipedia:Common knowledge
- Wikipedia:How to mine a source
- Wikipedia:Inaccuracy#Appendix: Reliability in the context
- Wikipedia:Independent sources
- Wikipedia:Identifying reliable sources (history)
- Wikipedia:Offline sources
- Wikipedia:Reliable sources/Cost
- Wikipedia:Reliable sources/Flaws
- Wikipedia:Potentially unreliable sources
- Wikipedia:Video links
- Wikipedia:Wikipedia clones
- Wikipedia:Reliable sources checklist provides a ref vetting method
- Wikipedia:Current science and technology sources
- Wikipedia:News sources
- Wikipedia:Reliable sources/Noticeboard – obtain community input on whether or not a source meets our reliability standards for a particular use
- Wikipedia:Wikipedia Signpost/2008-06-26/Dispatches – Signpost article
- Wikipedia:WikiProject Fact and Reference Check
- Change detection and notification
- Source criticism
- Wikipedia:WikiProject Resource Exchange/Resource Request
- Examples include The Creation Research Society Quarterly and Journal of Frontier Science (the latter uses blog comments as peer review).
- Please keep in mind that any exceptional claim would require exceptional sources, and this is policy.
- Princeton (© 2011). "Book reviews" (in English) (html). Scholarly definition document. Princeton. http://wordnetweb.princeton.edu/perl/webwn?s=book%20review. Retrieved September 22, 2011.
- Virginia Polytechnic Institute and State University (© 2011). "Book reviews" (in English) (html). Scholarly definition document. Virginia Polytechnic Institute and State University. http://www.lib.vt.edu/find/byformat/bookreviews.html. Retrieved September 22, 2011.
- A variety of these incidents have been documented by Private Eye and others and discussed on Wikipedia, where incorrect details from articles added as vandalism or otherwise have appeared in newspapers
- How to Read a Primary Source, Reading, Writing, and Researching for History: A Guide for College Students, Patrick Rael, 2004.
- How to Read a Secondary Source, Reading, Writing, and Researching for History: A Guide for College Students, Patrick Rael, 2004.
- Munroe, Randal (16 November 2011). "Citogenesis (Where citations come from)". xkcd. http://xkcd.com/978/. — a cautionary tale.