This page documents an English Wikipedia [[:Category:Wikipedia WP:RSs| WP:RS]]. Editors should generally follow it, though exceptions may apply. Substantive edits to this page should reflect consensus. When in doubt, discuss first on the talk page.

[[Category:Wikipedia wp:rss|Reliable sources]]

Wikipedia articles should be based on reliable published sources. This page provides guidance about how to identify reliable sources. Some of the relevant policy pages are No original research and Verifiability.

Any material that is challenged or likely to be challenged needs a source, and the responsibility for finding a source lies with the person who adds or restores the material. Unsourced or poorly sourced edits may be challenged and removed at any time. Sometimes it is better to have no information at all than to have information without a source.

Examples and discussions on sourcing by subject area can be found at this supporting page.

Sources 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. See Wikipedia:Copyrights.

Using reliable sources assures the reader that what is being presented meets the Wikipedia standards for verifiability, originality, and neutrality. Accurate citation allows the reader to go to those sources and gives appropriate credit to the author of the work.

Assessing the reliability of the sources used in an article allows the editor to caveat the statements made, identifying where weaknesses are present and where there may be alternative positions on a statement, with a qualitative opinion presented on the relative arguments based on the quality of sources.

If all the sources for a given statement or topic are of low reliability, this suggests to the reader that the content be treated with a degree of skepticism, and to the editor that the material may not be suitable for inclusion in Wikipedia.

Wikipedia relies heavily upon the established literature created by scientists, scholars and researchers around the world. Items that fit this criterion can always be considered reliable. However they may be outdated by more recent research, or controversial in the sense there are alternative scholarly explanations.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.
• In articles on religions and religious practices, religious scholars (recognized authorities on the religion) are considered reliable sources for the religion's practices and beliefs, and traditional religious and academic views of religious practices should generally both be cited and attributed as such when they differ.

Some criteria that can assist editors in evaluating non-scholarly sources:

• Attributability—The more we know about the originator, either organisation or individual, of source material, the better. This helps us measure the authority of the content.

• Expertise of the originator about the subject—An academic expert in one subject is more reliable when writing about that subject than when writing about another. For example, a biologist is more reliable when writing about biology than when writing about nuclear physics.

• Bias of the originator about the subject—If an author has some reason to be biased, or admits to being biased, this should be taken into account when reporting his or her opinion. This is not to say that the material is not worthy of inclusion, but please take a look at our policy on Neutral point of view.

• Editorial oversight—A publication with a declared editorial policy will have greater reliability than one without, since the content is subject to verification. Self published sources such as personal web pages, personally published print runs and blogs have not been subject to any form of independent fact-checking and so have lower levels of reliability than published news media (e.g. The Economist) and other sources with editorial oversight, which is less reliable itself than professional or peer reviewed journal (e.g. Nature).

• Replicability—The conclusions of the source can be reached using the information available and there is no indication of gaps in the thinking or process of derivation. Essentially, this criterion asks if there are any leaps of faith in the source.

• Declaration of sources—A source which is explicit about the data from which it derives its conclusions is more reliable than one which does not. Ideally, a source should describe the collection process and analysis method.

• Confidentiality—Sources which are considered confidential by the originating publisher may hold uncertain authority. Given that the original cannot be used to validate the reference, these should be treated with caution.

• Corroboration—The conclusions match with other sources in the field which have been derived independently. If two or more independent originators agree, in a reliable manner, then the conclusions become more reliable. Care must be taken to establish that corroboration is indeed independent, to avoid an invalid conclusion based on uncredited origination.

• Recognition by other reliable sources—A source may be considered more reliable if another source which is generally considered reliable cites or recommends it. Sources which have been attacked, or have rarely or never been cited, may be more suspect.

• Age of the source and rate of change of the subject—Where a subject has evolved or changed over time, a long standing source may not be accurate with respect to the current situation. To interpret utility one must appreciate how the subject has changed and if that change has impacted any of the salient points of the source information. Historical or out-of-date sources may be used to demonstrate evolution of the subject but should be treated with caution where used to illustrate the subject. If no newer sources are available, it is reasonable to caveat use of sources with an indication of the age and the resulting reduction in reliability.

• Persistence— If a reader goes to the cited source to validate a statement, or to gain further understanding of the topic, the form cited should remain stable, continuing to contain the information used by the editor to support the words. In this sense a book or journal citation is superior to an online source where the link may become broken. Some web resources have editorial policies which lead to a lack of persistence; therefore, web citations should be treated with caution.

These issues are particularly pertinent to Wikipedia where various editors involved in an article may have their own expertise or position with respect to the topic. Not all sources on a topic are equally reliable, and some sources will have differing degrees of reliability in different contexts.

In general, a topic should use the most reliable sources available to its editors. Common sense is required to determine what sources to use; this guideline cannot be applied robotically. If you have questions about a source's reliability, discuss with other editors on the article's talk page, or if the source is already used in the article, you can draw attention to it with the ((unreliable)) template.

Certain 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 reputable 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 credible and verifiable sources, especially with regard to historical events, politically-charged issues, and biographies of living people.

For guidance related to the creation of entire articles about said topics, see Wikipedia:Fringe theories.

Three classes of sources exist, each of which can be used within Wikipedia:

• A primary source is a document or person providing direct evidence of a certain state of affairs; in other words, a source very close to the situation you are writing about. The term mainly refers to a document produced by a participant in an event or an observer of that event. Primary sources include official reports, letters, eyewitness accounts, autobiographies, statistics compiled by authoritative agencies, and court records. Experts usually have advanced training, and use as many different primary sources as are available so they can be checked against each other. Thus, primary materials typically require interpretation, interpolation, extrapolation, or corroboration, each of which usually constitutes original research. Wikipedia articles may use primary sources, so long as they have been published by a reputable publisher, but only to make descriptive points about the topic. Any interpretive claims require secondary sources.

• Secondary—The informed and expert interpretation, interpolation, extrapolation or corroboration of primary sources to synthesize a conclusion. In general, Wikipedia articles should rely on reliable secondary sources.

• Tertiary—Summarized material drawn from secondary sources, as in general encyclopedias. These sources generally lack adequate coverage of the topic to be considered comprehensive where arguments are subtle and nuanced. They generally do not discuss and evaluate alternative interpretations. Tertiary sources can be used for names, spellings, locations, dates and dimensions. Some tertiary sources are more reliable than others, and within any given teriary 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. Unsigned articles may be less reliable, but they may be used so long as the encyclopedia is a high quality one.

Unsourced or poorly sourced contentious material about living persons should be removed immediately and should not be moved to the talk page.^[1]

Anyone can create a website or pay to have a book published and then claim to be an expert in a certain field. For that reason, self-published books, personal websites, anonymous websites, and blogs are largely not acceptable as sources. See below for exceptions.

Posts to bulletin boards, Usenet, and wikis, or messages left on blogs, should not be used as sources. This is in part because we have no way of knowing who has written or posted them, and in part because there is no editorial oversight or third-party fact-checking. See self-published sources for exceptions.

A self-published source is a published source that has not been subject to any form of independent fact-checking, or where no one stands between the writer and the act of publication. It includes personal websites and books published by vanity presses. Anyone can create a website or pay to have a book published, and 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.

When a well-known, professional researcher writing within his or her field of expertise, or a well-known professional journalist, has produced self-published material, these may be acceptable as sources, so long as his or her work has been previously published by credible, third-party publications. Editors should exercise caution for two reasons: first, if the information on the professional researcher's blog (or self-published equivalent) is really worth reporting, someone else will have done so; second, the information has been self-published, which means it has not been subject to any independent form of fact-checking.

Self-published material, whether published online or as a book or pamphlet, may be used as sources of information about the author, so long as there is no reasonable doubt who wrote the material, and so long as it is:

• relevant to the self-publisher's notability;
• not contentious;
• not unduly self-serving or self-aggrandizing;
• about the subject only and not about third parties or events not directly related to the subject;

The reputation of the self-publisher is a guide to whether the material rises to the level of notability at all.

Personal websites, blogs, and other self-published or vanity publications should not be used as secondary sources. That is, they should not be used as sources of information about a person or topic other than the owner of the website, or author of the book. The reason personal websites are not used as secondary sources — and as primary sources only with great caution and not as a sole source if the subject is controversial — is that they are usually created by unknown individuals who have no one checking their work. They may be uninformed, misled, pushing an agenda, sloppy, relying on rumor and suspicion, or even insane; or they may be intelligent, careful people sharing their knowledge with the world. Only with independent verification by other sources not holding the same POV is it possible to determine the difference.

Visiting a stranger's personal website is often the online equivalent of reading an unattributed flyer on a lamp post, and should be treated accordingly.

The websites, print media, and other publications of political parties and religious groups should be treated with caution, although neither political affiliation nor religious belief is in itself a reason not to use a source.

Extremist organizations and individuals, whether of a political, religious, racist, or other character, should be used only as primary sources; that is, they should only be used as sources about themselves and their activities, and even then should be used with caution.

Also see Wikipedia:Convenience links

The 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. For example, an editor providing a citation to Adam Smith's famous work The Wealth of Nations might choose to include both a citation to a published copy of the work and a link to the work on the internet, as follows:

Smith, Adam (1904) [1776]. ed. Edwin Cannan (ed.). The Wealth of Nations (Fifth edition ed.). London: Methuen and Co. ((cite book)): |edition= has extra text (help); |editor= has generic name (help), available at Wikisource

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, amendations, 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.

Just as underlying facts must be sourced, claims of consensus must be sourced in the presence of differences of opinion. Claims that "most" or "all" scientists, scholars, ministers (or rabbis or imams etc.) of a religious denomination, voters, etc. hold a view require sourcing, particularly on matters that are subject to dispute. In the absence of a reliable source of consensus or majority view, opinions should be identified as those of the sources.

See Wikipedia:Reliable sources/examples for examples and discussion on 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.

• Wikipedia:Check your facts, style guide
• Wikipedia:Common knowledge, guideline
• Wikipedia:Independent sources, essay
• Wikipedia:WikiProject Fact and Reference Check

• 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.