It can be difficult to know where to begin - and when to end - a grey literature search. Some considerations when developing a grey literature search strategy include:
Who would likely have written about your topic?
What kinds of literature would help answer your research question?
Which time periods or geographic areas are relevant to your research?
Preprints are manuscripts which may have been submitted to a journal, but not yet published. They have not yet gone through a formal peer review process, but some preprint servers do allow other researchers to post comments.
Cochrane's CENTRAL database includes many results from clinical trials registries, but for a complete search, you may need to search registries directly.
Clinical study reports are extensive documents produced by pharmaceutical companies for regulatory agencies such as Health Canada, the FDA or EMA. Sometimes summaries of clinical study reports are available online, but obtaining the full report may not be possible.
Some pharmaceutical companies are now allowing researchers more access to the data included in CSRs and ongoing clinical trials. For more information see: