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Stage 2: Developing the Search: Searching Grey Literature

Grey Literature

The organization of grey literature refers it to work that is:

"…produced on all levels of government, academics, business and industry in print and electronic formats, but which is not controlled by commercial publishers."

For a brief summary of grey literature, watch our video below.


Why is Grey Literature Important to Include in a Review?

Because grey literature is not published through traditional sources, it is often missed from database searches. They are important to include because they are accessible earlier than peer-reviewed publications, and they include relevant studies that may not get published (e.g., studies with negative or null results).

Hopewell et al. (2007) found that systematic reviews that integrated (vs. did not integrate) grey literature significantly affected the outcome of the review, as published trials tended to exhibit larger treatment effects than grey trials.

Grey literature is therefore important to:

How do I Identify and Locate Grey Literature Relevant to my Review?

Searching grey literature can be challenging. For some direction on what kinds of grey literature are relevant to addressing your research question, consider the following:

Other things to consider when choosing grey literature are:

GreyNet International provides an extensive (though not comprehensive) list of the types of grey literature.​