Primary literature consists of articles based on new data or presenting new analyses and interpretations of existing data, published in peer-reviewed journals. By "peer review," we mean that a paper submitted for publication has been reviewed and approved by several other scientists before publication. Primary literature in mainstream scientific journals should constitute the majority of the sources of information for your term paper.  (Some book chapters in edited book volumes also fall into the primary literature category.  Your instructor can help you determine whether this is the case for any book chapters you use).

Review literature is a kind of "secondary" or "derivative" literature, in the sense that review articles do not present new data or analyses but instead summarize and synthesize the information already available about a topic. These are also acceptable for use in your paper, as long as they have been published by established scientists in peer-reviewed journals or in book-type compilations of papers.

Unreviewed literature is found in popular magazines, newspapers, and on the Web (Internet). In general, you should place little faith in any information presented in those forums, and in your term paper you should not use information obtained that way.  Some popular natural history magazines (e.g. Natural History, Discover, Scientific American, American Scientist) are good sources when browsing for term paper ideas, but are not appropriate sources for citation in the term paper itself.  In general, if information in a popular source is scientifically accurate, there will be primary literature that reports the original data, which should be read and used for the term paper.

The Web should be avoided except as a way to find links to confirmed information in journals and books. You must read the article in the journal or book, once located, to make sure it really says what the web suggests it says.  In rare cases, it may be appropriate to cite a web site in your paper.  Check with your W instructor if you think you have one of these rare cases!