Gray literature – using non-peer reviewed sources


Gray Welsh Cob by bambe1964 Attribution-NoDerivs Licence

Conference proceedings and textbooks are often good sources to find out what experts are thinking in a discipline. Some conference proceedings also provide the early reports of new scientific findings that might be pertinent to your work. However you need to cite non-peer reviewed literature sparingly, if at all.

One time when you may wish to cite textbooks or conference proceedings is when you need to support statements about another author’s opinion. In that case make it clear that you are citing opinion and not empirical published observations. Another time is when the research is so new it is only available in a conference proceedings abstract. In this case be very sure that you have checked thoroughly for the peer-reviewed version of the publication and you should only be citing very recent conference abstracts in this case (less than 2 years old).

Remember to distinguish the peer-reviewed and non-peer-reviewed literature carefully in your review. The reader needs to be able to tell if you are citing non-peer reviewed material.


  1. Hi Liz! Thank you for your posts, always enlightening and helpful. I am a bit concerned about this. A lot of my references are from non peer-reviewed sources, usually pointing out that things that CAM peddlers say is not purely my own opinion. Do you know of a way to separate my references list into a peer-reviewed references list and a non peer-reviewed references list. I thought Word or Endnote would have a function to created a references list and a bibliography separately, but I cannot find one. How would you recommend pointing out that a reference is not peer-reviewed? Maybe an asterisk by all non-peer-reviewed citations and references?
    Cheers, Simon.


    • Hi Simon,
      Now that you are aware of this issue you will start noticing more how other authors handle it and get better at doing it yourself. In the text you can use constructions that make it clear you are citing non-peer reviewed material. For example if you are citing findings presented only in abstract form you might say so in the sentence. If you are citing the opinions of experts in textbooks you might use words like “Common recommendations are……”. The writing will also convey it by contrast because for research studies you will be saying things like “In a retrospective survey of 150 people…”, thus making it more obvious when other things are not research.

      There is no need to separate it out in the reference list.


Leave a comment

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s