WikiIslam:Reliable Sources
Types of Sources
Primary Sources
Primary sources are those such as the Qur'an, hadiths, and in an article about a book it would be the book itself. In the case of a person, it would be the subject itself; if John Doe said something about himself, his statement would be a primary source.
In order to allow greater leeway in criticism of Islam, primary sources are not limited and may be freely used in articles. In other words, an editor should not remove a primary-sourced statement by asserting that primary sources are to be avoided.
Secondary Sources
Secondary sources are typically based primary sources. For example, a statement by a scholar about a certain battle in the history of Islam would be a secondary source. The news articles "Fort Hood suspect condemned '09 shootings" and "Outcry over Malaysian child marriages" that report on a development or an incident are also secondary sources. One is encouraged to use secondary sources.
Tertiary Sources
Tertiary sources are sources that rely upon primary and secondary sources. The Columbia Encyclopedia would be an example. They may be used as well. There are a variety of encyclopedias.