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Grey Literature:  


This guide is intended to create awareness of the importance of grey literature in health research, by providing an overview of what this body of literature refers to, introduce common document types, explore where it can be found, and learn how it can be evaluated. We also have some tips for searching with Google.

To learn more, please see our Introduction to Grey Literature online course.

Common Document Types

There are many types of grey literature, but below are some of the most common in the health sciences:

Grey Literature Overview

What is grey literature?

“information produced on all levels of government, academics, business and industry in electronic and print formats not controlled by commercial publishing, where publishing is not the primary activity of the producing body”     
   Source: ICGL Luxembourg definition, 1997. Expanded in New York, 2004 

Why should grey literature be searched?

  • Grey literature is an important supplement to database searching,
  • Grey literature often focuses on unique content that may be overlooked with mainstream commercial academic publishers, such as clinical trials that are unpublished due to negative consequences, loss to follow-up, etc
  • Grey literature is rapidly produced and instantly available the moment it is created, since it avoids the peer-review process

When should grey literature be searched?

  • When you are seeking out a specific framework, guideline, policy, pathway, or tool.


In 2010, Jess Tyndall, a librarian at Flinders University, Australia created AACODS, a checklist for evaluating and critically appraising grey literature resources.  Below is a brief summary of the complete checklist and what the AACODS acronym stands for: 

Searching with Google: Tips & Tricks

Despite the benefits of supplementing a database search with additional grey literature resources, finding grey material can be a challenge. Often grey literature may not be available online, and if it is it, it may be missing important information to help with findability on the web.

The following are a few tips to assist when using Google to search for material of a grey nature: