Wikipedia articles should be based on reliable, published sources. This page is a guideline, not a policy: The relevant policies on sources are Wikipedia:Verifiability and Wikipedia:No original research, and additional restrictions in biographies of living people.
Wikipedia:Verifiability says that any material that is challenged or likely to be challenged needs a source, as do quotations, and the responsibility for finding a source lies with the person who adds or restores the material. Sometimes it is better to have no information than to have information without a source.
See Wikipedia:Verifiability/Noticeboard for queries about the reliability of particular sources; see Wikipedia talk:Verifiability for queries about the policy.
What is a reliable source?
editA reliable source is a published work regarded as trustworthy or authoritative in relation to the subject at hand. Evaluation of reliability will depend on the credibility of the author and the publication, along with consideration of the context. Reliable publications are those with an established structure for fact-checking and editorial oversight. A world-renowned mathematician may not be a reliable source about biology. Authors may be reliable outside their primary field if recognized as having expertise in a secondary area of study. In general, an article should use the most reliable and appropriate published sources to cover all majority and significant-minority published views, in line with Wikipedia:Neutral point of view.
Articles should rely on reliable, third-party published sources with a reputation for fact-checking and accuracy. Sources should be appropriate to the claims made: exceptional claims require exceptional sources. All articles must adhere to Wikipedia's neutrality policy, fairly representing all majority and significant-minority viewpoints that have been published by reliable sources, in rough proportion to the prominence of each view.[1]
In general, the most reliable sources are peer-reviewed journals and books published in university presses; university-level textbooks; magazines, journals, and books published by respected publishing houses; and mainstream newspapers. As a rule of thumb, the greater the degree of scrutiny involved in checking facts, analyzing legal issues, and scrutinizing the evidence and arguments of a particular work, the more reliable it is.
Academic and peer-reviewed publications are highly valued and usually the most reliable sources in areas where they are available, such as history, medicine and science. Material from reliable non-academic sources may also be used in these areas, particularly if they are respected mainstream publications. The appropriateness of any source always depends on the context. Where there is disagreement between sources, their views should be clearly attributed in the text.
Sources with a poor reputation for fact-checking or with no editorial oversight should only be used in articles about the sources themselves. Articles about such sources should not repeat any contentious claims the source has made about third parties, unless those claims have also been published by reliable sources.
Why use reliable sources?
editSources are used:
- To support an assertion made in an article. Sources used in this manner should be directly referenced for the point that is being supported.
- To give credit to the source, to avoid the appearance of plagiarism or copyright violations.
If all the sources for a given statement or topic are of low reliability, the material may not be suitable for inclusion in Wikipedia.
Aspects of reliability
editArticles should rely on reliable, third-party published sources with a reputation for fact-checking and accuracy. Sources should be appropriate to the claims made.
Scholarship
editWikipedia relies heavily upon the established literature created by scientists, scholars and researchers around the world. Items that fit this criterion are usually considered reliable. However, they may be outdated by more recent research, or controversial in the sense that there are alternative scholarly explanations. Wikipedia articles should point to all major scholarly interpretations of a topic.
- The material has been thoroughly vetted by the scholarly community. This means published in peer-reviewed sources, and reviewed and judged acceptable scholarship by the academic journals.
- Items that are recommended in scholarly bibliographies are preferred.
- Items that are signed are more reliable than unsigned articles because it tells whether an expert wrote it and took responsibility for it.
Exceptional claims require exceptional sources
editCertain red flags should prompt editors to examine the sources for a given claim.
- Surprising or apparently important claims that are not widely known.
- Surprising or apparently important reports of recent events not covered by reliable news media.
- Reports of a statement by someone that seems out of character, embarrassing, controversial, or against an interest they had previously defended.
- Claims not supported or claims that are contradicted by the prevailing view in the relevant academic community. Be particularly careful when proponents say there is a conspiracy to silence them.
Exceptional claims should be supported by multiple high quality reliable sources, especially regarding scientific or medical topics, historical events, politically charged issues, and in material about living people.
Original research is not a reliable source
editWikipedia should not be the original source for new research, ideas, interpretations, or analyses. Such original research has not yet been published in a reliable source, and therefore is not suitable for inclusion in Wikipedia. When citing reliable sources, editors must ensure that the sources are not interpreted or analyzed in a novel or non-obvious way.
Biographies of living persons
editMaterial about living persons must be sourced very carefully. Without reliable third-party sources, a biography will violate the No original research and Verifiability policies, and could lead to libel claims.
Self-published sources
editSelf-published books, personal websites, and blogs are largely not acceptable as sources. They may, in some circumstances, be acceptable when produced by an established expert on the topic of the article whose work in the relevant field has previously been published by reliable third-party publications, but such use is discouraged. Self-published sources should never be used as third-party sources about living persons, even if the author is a well-known professional researcher or writer; see WP:BLP#Reliable sources. Articles and posts on Wikipedia or other open wikis should never be used as third-party sources. Material from self-published and questionable sources may be used as sources in articles about themselves, but only under certain conditions; see WP:SELFPUB for the details.
Extremist sources
editOrganizations and individuals that are widely acknowledged as extremist, whether of a political, religious or anti-religious, racist, or other nature, should be used only as sources about themselves and their activities in articles about themselves, and even then with caution.
Claims of consensus
editClaims of consensus must be sourced. The claim that all or most scientists, scholars, or ministers hold a certain view requires a reliable source. Without it, opinions should be identified as those of particular, named sources.
Convenience links
editThe term "convenience link" is typically used to indicate a link to a copy of a resource somewhere on the Internet, offered in addition to a formal citation to the same resource in its original format. Such links are unique in how reliability is applied. It is important to ensure that the copy being linked is a true copy of the original, without any comments, emendations, edits or changes. When the "convenience link" is hosted by a site that is considered reliable on its own, this is relatively easy to assume. However, when such a link is hosted on a less reliable site, the linked version should be checked for accuracy against the original, or not linked at all if such verification is not possible.
Examples
editSee Wikipedia:Reliable sources/examples for examples of the use of statistical data, advice by subject area (including history, physical sciences, mathematics and medicine, law, Business and Commerce, popular culture and fiction), and the use of electronic or online sources.
See also
editExternal links
edit- 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.
Footnotes
edit- ^ Tiny-minority views and fringe theories need not be included, except in articles devoted to them.
Primary, secondary, and tertiary sources
editResearch that consists of collecting and organizing material from existing sources within the provisions of this and other content policies is encouraged: this is "source-based research," and it is fundamental to writing an encyclopedia. However, care should be taken not to "go beyond" the sources or use them in novel ways. Sources may be divided into three categories:
- Primary sources are documents or people very close to the situation being written about. An eyewitness account of a traffic accident is a primary source. United Nations Security Council resolutions are primary sources. Primary sources that have been published by a reliable source may be used in Wikipedia, but only with care, because it is easy to misuse them. For that reason, anyone—without specialist knowledge—who reads the primary source should be able to verify that the Wikipedia passage agrees with the primary source. Any interpretation of primary source material requires a secondary source. Examples of primary sources include archeological artifacts; photographs; historical documents such as diaries, census results, video or transcripts of surveillance, public hearings, trials, or interviews; tabulated results of surveys or questionnaires; written or recorded notes of laboratory and field experiments or observations; and artistic and fictional works such as poems, scripts, screenplays, novels, motion pictures, videos, and television programs.
- Secondary sources draw on primary sources to make generalizations or interpretive, analytical, or synthetic claims. A journalist's story about a traffic accident or a Security Council resolution is a secondary source, assuming the journalist was not personally involved in either. An historian's interpretation of the decline of the Roman Empire, or analysis of the historical Jesus, is a secondary source. Wikipedia articles should rely on reliable, published primary and secondary sources.
- Tertiary sources are publications such as encyclopedias that sum up other secondary sources, and sometimes primary sources. (Wikipedia itself is a tertiary source.) Some tertiary sources are more reliable than others, and within any given tertiary source, some articles may be more reliable than others. For example, articles signed by experts in Encyclopaedia Britannica and encyclopedias of similar quality can be regarded as reliable secondary sources instead of tertiary ones. Unsigned articles may be less reliable, but they may be used so long as the encyclopedia is a high quality one.
An article or section of an article that relies on a primary source should (1) only make descriptive claims, the accuracy of which is easily verifiable by any reasonable, educated person without specialist knowledge, and (2) make no analytic, synthetic, interpretive, explanatory, or evaluative claims. Contributors drawing on primary sources should be careful to comply with both conditions.
Sources
editArticles should rely on reliable, third-party published sources with a reputation for fact-checking and accuracy. Sources should be appropriate to the claims made: exceptional claims require exceptional sources. All articles must adhere to Wikipedia's neutrality policy, fairly representing all majority and significant-minority viewpoints that have been published by reliable sources, in rough proportion to the prominence of each view.[1]
In general, the most reliable sources are peer-reviewed journals and books published in university presses; university-level textbooks; magazines, journals, and books published by respected publishing houses; and mainstream newspapers. As a rule of thumb, the greater the degree of scrutiny involved in checking facts, analyzing legal issues, and scrutinizing the evidence and arguments of a particular work, the more reliable it is.
Academic and peer-reviewed publications are highly valued and usually the most reliable sources in areas where they are available, such as history, medicine and science. Material from reliable non-academic sources may also be used in these areas, particularly if they are respected mainstream publications. The appropriateness of any source always depends on the context. Where there is disagreement between sources, their views should be clearly attributed in the text.
Questionable sources
editQuestionable sources are those with a poor reputation for fact-checking or with no editorial oversight. Questionable sources should only be used in articles about themselves. (See below.) Articles about such sources should not repeat any contentious claims the source has made about third parties, unless those claims have also been published by reliable sources.
Self-published sources (online and paper)
editAnyone can create a website or pay to have a book published, then claim to be an expert in a certain field. For that reason, self-published books, personal websites, and blogs are largely not acceptable as sources.[2]
Self-published material may, in some circumstances, be acceptable when produced by an established expert on the topic of the article whose work in the relevant field has previously been published by reliable third-party publications. However, caution should be exercised when using such sources: if the information in question is really worth reporting, someone else is likely to have done so.
Self-published sources should never be used as third-party sources about living persons, even if the author is a well-known professional researcher or writer; see WP:BLP#Reliable_sources.
Articles and posts on Wikipedia or other open wikis should never be used as third-party sources.
Self-published and questionable sources in articles about themselves
editMaterial from self-published and questionable sources may be used as sources in articles about themselves, so long as:
- it is relevant to their notability;
- it is not contentious;
- it is not unduly self-serving;
- it does not involve claims about third parties;
- it does not involve claims about events not directly related to the subject;
- there is no reasonable doubt as to who wrote it;
- the article is not based primarily on such sources.
Sources in languages other than English
editBecause this is the English Wikipedia, for the convenience of our readers, English-language sources should be used in preference to foreign-language sources, assuming the availability of an English-language source of equal quality, so that readers can easily verify that the source material has been used correctly.
Keep in mind that translations are subject to error, whether performed by a Wikipedia editor or a professional, published translator. In principle, readers should have the opportunity to verify for themselves what the original material actually said, that it was published by a credible source, and that it was translated correctly.
Therefore, when the original material is in a language other than English:
- Where sources are directly quoted, published translations are generally preferred over editors performing their own translations directly.
- Where editors use their own English translation of a non-English source as a quote in an article, there should be clear citation of the foreign-language original, so that readers can check what the original source said and the accuracy of the translation.
Undue weight
editNPOV says that the article should fairly represent all significant viewpoints that have been published by a reliable source, and should do so in proportion to the prominence of each. Now an important qualification: Articles that compare views should not give minority views as much or as detailed a description as more popular views, and may not include tiny-minority views at all. For example, the article on the Earth only very briefly refers to the Flat Earth notion, a view of a distinct minority.
We should not attempt to represent a dispute as if a view held by a small minority deserved as much attention as a majority view. Views that are held by a tiny minority should not be represented except in articles devoted to those views. To give undue weight to a significant-minority view, or to include a tiny-minority view, might be misleading as to the shape of the dispute. Wikipedia aims to present competing views in proportion to their representation among experts on the subject, or among the concerned parties. This applies not only to article text, but to images, external links, categories, and all other material as well.
Undue weight applies to more than just viewpoints. Just as giving undue weight to a viewpoint is not neutral, so is giving undue weight to other verifiable and sourced statements. An article should not give undue weight to any aspects of the subject, but should strive to treat each aspect with a weight appropriate to its significance to the subject. Note that undue weight can be given in several ways, including, but not limited to, depth of detail, quantity of text, prominence of placement, and juxtaposition of statements.
Minority views can receive attention on pages specifically devoted to them—Wikipedia is not a paper encyclopedia. But on such pages, though a view may be spelled out in great detail, it must make appropriate reference to the majority viewpoint, and must not reflect an attempt to rewrite majority-view content strictly from the perspective of the minority view.
- From Jimbo Wales, paraphrased from this post from September 2003 on the mailing list:
- If a viewpoint is in the majority, then it should be easy to substantiate it with reference to commonly accepted reference texts;
- If a viewpoint is held by a significant minority, then it should be easy to name prominent adherents;
- If a viewpoint is held by an extremely small (or vastly limited) minority, it does not belong in Wikipedia (except perhaps in some ancillary article) regardless of whether it is true or not; and regardless of whether you can prove it or not.
Views held only by a tiny minority of people should not be represented as significant minority views, and perhaps should not be represented at all.
If you are able to prove something that no one or few currently believe, Wikipedia is not the place to premiere such a proof. Once a proof has been presented and discussed elsewhere, however, it may be referenced. See: Wikipedia:No original research and Wikipedia:Verifiability.
A vital component: good research
editDisagreements over whether something is approached neutrally can usually be avoided through the practice of good and unbiased research, based upon the best and most reputable authoritative sources available. Try the library for reputable books and journal articles, and look for the most reliable online resources. A little ground work can save a lot of time justifying a point later.
Sources
editReliable sources
editMaterial about living persons must be sourced very carefully. Without reliable third-party sources, a biography will violate the No original research and Verifiability policies, and could lead to libel claims.
Material about living persons available solely in questionable sources or sources of dubious value should be handled with caution, and, if derogatory, should not be used at all in biographies of living people, either as sources or via external links (see above).
Material from self-published books, zines, websites, and blogs should never be used as a source about a living person, unless written or published by the subject of the article (see below).
Editors should avoid repeating gossip. Ask yourself whether the source is reliable; whether the material is being presented as true; and whether, even if true, it is relevant to an encyclopedia article about the subject. When less-than-reliable publications print material they suspect is untrue, they often include weasel phrases. Look out for these. If the original publication doesn't believe its own story, why should we?
Editors should also be careful of a feedback loop in which an unsourced and speculative contention in a Wikipedia article gets picked up, with or without attribution, in an otherwise-reliable newspaper or other media story, and that story is then cited in the Wikipedia article to support the original speculative contention.
Remove unsourced or poorly sourced contentious material
editEditors should remove any contentious material about living persons that is unsourced, relies upon sources that do not meet standards specified in Wikipedia:Verifiability, or is a conjectural interpretation of a source (see Wikipedia:No original research). If the material is derogatory and unsourced or poorly sourced, the three-revert rule does not apply to its removal. Content may be re-inserted when it conforms to this policy.
These principles apply to biographical material about living persons found anywhere in Wikipedia, including user and talk pages. Administrators may enforce the removal of such material with page protection and blocks, even if they have been editing the article themselves. Editors who re-insert the material may be warned and blocked. See the blocking policy and Wikipedia:Libel.
Administrators encountering biographies that are unsourced and negative in tone, where there is no neutral version to revert to, should delete the article without discussion (see Wikipedia:Criteria for speedy deletion criterion G10 for more details).
Jimmy Wales has said it is better to have no information at all than to include speculation, and he has emphasized the need for sensitivity:
I can NOT emphasize this enough. There seems to be a terrible bias among some editors that some sort of random speculative 'I heard it somewhere' pseudo information is to be tagged with a 'needs a cite' tag. Wrong. It should be removed, aggressively, unless it can be sourced. This is true of all information, but it is particularly true of negative information about living persons.[3]
Using the subject as a self-published source
editSelf-published material may never be used in BLPs unless written by the subject him or herself. Subjects may provide material about themselves through press releases, personal websites, or blogs. Material that has been self-published by the subject may be added to the article only if:
- it is relevant to the subject's notability;
- it is not contentious;
- it is not unduly self-serving;
- it does not involve claims about third parties;
- it does not involve claims about events not directly related to the subject;
- there is no reasonable doubt as to who wrote it;
- the article is not based primarily on such sources.
These provisions do not apply to subjects' autobiographies that have been published by reliable third-party publishing houses; these are treated as reliable sources like any other, because they are not self-published.
A blog or personal website self-published by the subject may be listed in the external links/further reading section if not used as a source in the article.
- ^ Tiny-minority views and fringe theories need not be included, except in articles devoted to them.
- ^ "Blogs" in this context refers to personal and group blogs. See e.g., Wikipedia:Articles_for_deletion/The_Game_(game)_(6th_nomination) for an often-cited example deletion discussion covering this matter. Some newspapers host interactive columns that they call blogs, and these may be acceptable as sources so long as the writers are professionals and the blog is subject to the newspaper's full editorial control. Where a news organization publishes the opinions of a professional but claims no responsibility for the opinions, the writer of the cited piece should be phrasally attributed (e.g. "Jane Smith has suggested..."). Posts left on these columns by readers may never be used as sources.
- ^ Cite error: The named reference
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