Wikipedia:Reliable sources

For a list of sources that are talked about often, see Wikipedia:Reliable sources/Perennial sources.

One of the problems that Wikipedia is most criticized for is that it is not always reliable. This is true, since anybody can change most articles and add anything they like. Sometimes bad changes stay in place for a long time. Wikipedia guidelines such as Wikipedia:Verifiability and Wikipedia:No original research and the additional restrictions for living people at Wikipedia:Biographies of living persons have been made to help prevent this.

These guidelines are there for two reasons:

• They help make sure that information which is added is true, or at least that it is not made up on the spot.
• They show us that a topic has received attention from other people, and this helps show and argue notability.

However, many sources are not suitable for use in Wikipedia because they are not reliable.

This is a guideline about the types of sources which are reliable. Wikipedia articles should use reliable, third-party, published sources. (An article is a page in the main namespace. Most other pages, such as Wikipedia's policies and guidelines, do not need sources.) These sources can be in any language, not just English or Simple English.

What is a reliable source?

See also: WP:Help with sources

Sources used in Wikipedia should have been published. Some published documents are written by just one person, and nobody else checks it before it is published. It is easy for these sources to contain mistakes or untrue information. Other documents are written by people who have studied the subject for many years, and many other people have read them carefully to make sure that the information is correct. Although both kinds of documents can contain things that are not true, documents that people have checked are more likely to contain correct information and to reflect the most common views on a subject. These are called reliable sources.

How reliable a source is depends on context. Some publishers like the BBC become well known for having a reliable publication process. This means that they only publish documents after they check them carefully. As a guide, the more people who help with checking facts, analyzing legal issues, and examining the writing, the more reliable the publication.

How do I use sources?

Wikipedia:Citing sources has help with how to add sources to an article. If you are using Firefox, Cite4wiki is a useful tool which will make adding sources much easier.

Sources should directly support the information as it is presented in an article and should be appropriate to the claims made; if an article topic has no reliable sources, Wikipedia should not have an article on it.

Wikipedia articles should cover all major and significant-minority views that have been published by reliable sources. See Wikipedia:Neutral point of view.

What kind of sources should I use?

The best kind of sources for Wikipedia are reliable, third-party sources (not published by or related to the subject of the article). Wikipedia:Help with sources has more information about these and why they are needed. Unfortunately, the Simple English Wikipedia has many articles which do not have these kinds of sources, or in fact any sources at all.

Here are some examples of useful places to find sources like this:

• The BBC and National Geographic websites, and those of other well-respected publications.
• Academic databases like JSTOR, but these are often only available to people who are students at certain universities.
• Google Books and Google Scholar often have many useful books and papers.
• Newspapers such as The Wall Street Journal and The Daily Telegraph, but be careful to avoid articles which express the writer's feelings and opinions, not facts. These often have a title of "editorial", "op-ed" or "opinion".

Often, it is helpful just to run a search using a search engine, and avoid websites that are not reliable.

What kind of sources should I avoid?

Internet

Many websites are not reliable sources. If a website is written by just one person, it is often that person's opinion or their own point of view. This may not be completely correct. If a website is selling a product or promoting something, it is not a reliable source, as the information provided is there to help make money. The best websites are those that are run by newspapers or other media agencies that are known to be trustworthy, or those which have a reputation for providing good information.

Some websites that should be avoided are:

• Social networking websites like Facebook and Myspace
• Websites which are selling products

A useful thing to look out for is the number of emotive words a source uses. If they use many words like "wonderful" or "terrible", they may not have a neutral point of view. Sources which are not neutral may sometimes be showing only one side of the facts, which is not useful unless you are writing about opinions which people have.

Books

Part of the problem is the fact that many reliable, academic sources do not write about subjects in the simple way that is required for this Wikipedia. Sometimes it is very difficult to translate the meaning of these difficult texts into simple words. Many users who write articles simply use websites or books that are already written for children or people learning English. This is a problem, because these sources tend to simplify things so much that they are no longer completely accurate. When a Wikipedia user rewrites the information in these sources in their own words, the meaning may be different from what is true.

Sources linked to the subject

Be careful with sources which are written by someone who represents or is the subject. These people have a conflict of interest. In general, if a person or organization writes about itself, this writing is not a good source. Such sources often support the subject's point of view and not a neutral point of view. However, that does not mean these sources should be avoided, because often it is only the people close to the subject who know some of the facts about it. A self-published source can be used if all of the following are true:

1. the material is not too biased on the subject;
2. it does not involve claims about third parties (such as people, organizations, or other entities);
3. it does not involve claims about events not directly related to the subject;
4. there is no reasonable doubt as to whether it was written by the subject;
5. the Wikipedia article is not based mainly on such sources.

What should I do if I find an article that has no sources?

Be bold! If you can find sources for the information in the article, please do add them. Wikipedia:Citing sources has help with how to do this.

If you are not able to add sources, you can place a {{unreferenced}} tag on it. This will add it to a category of unreferenced pages that need to be fixed. This is not as helpful, because most users do not check the list of unreferenced pages for work to do.

If an article looks like it is probably a hoax or not true, please do not add {{unreferenced}}. Instead, it should be deleted. If it is obviously not true, it can be deleted quickly by placing {{QD|A6}}. If it is not as clear, you can nominate it for deletion here.

What if it is just one statement that is unsourced?

If an article has some sources, but it also has some statements that may not be true and are not sourced, you can place {{fact}} after them to show that they do not have a source. However, if the information is clearly false, or if the article is about a living person, it is best to simply remove it.

Reliable sources in science

Reliable sources in science need to be 1. Reliable 2. Secondary.

Reliable: published in a reputable journal (e.g. Nature, Science...) or (if a book), by a reputable scientist and a reputable publisher. This is because reputable publishers employ qualified readers to critique manuscripts, and have a reputation to uphold.
Websites are reputable if (and only if) they have independent editorial supervision. So a website of the University of California at Berkeley which supports a course is reliable because it has the particular department's supervision behind it.

Secondary: A primary source is one which announces an original finding or opinion of some kind. Generally (there may be exceptions) such papers are too specialised for our purposes. They may need to be interpreted by an expert in the field. Secondary sources are surveys and interpretations by experts in the particular field. Reviews and surveys in Nature and similar journals; university-level textbooks, semi-popular accounts if written by experts (e.g. Einstein & Infield's Theory of relativity; Mayr's What evolution is).
Tertiary sources are such as articles in the press, most books for children, popular books by authors who are not experts. They are not suitable for references in scientific topics because their reliability is open to question.

A good source will combine both reliability and appropriate breadth. So, a leading encyclopedia has articles by renowned experts and supervised by an editorial team. That makes it a suitable source for reference in one of our scientific topics. Any reference to a website which does not have a similar backing is open to question.

These guidelines are written with science in mind, but would probably apply to many other scholarly areas.

Fringe theories

Fringe theories are ideas about a subject that most people who know a lot about that subject would strongly disagree with. Some examples of fringe theories are conspiracy theories and ideas about science that do not have much scientific support. Books and websites that promote fringe theories are usually not considered reliable sources, unless they are being used in an article about those fringe theories. For example, the Simple English Wikipedia has an article about the Flat Earth Society, which claims that the Earth is flat, but the Flat Earth Society's website is not used as a source in the article about the Earth, because it is not considered to be a reliable source. For more information, see en:WP:FRINGE on the English Wikipedia.

Related pages

• {{fact}} — adds:
• Wikipedia:Citing sources
• Wikipedia:Fringe theories (on the English Wikipedia)
• Wikipedia:No original research

Other websites

• 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.