Contact your subject librarian for tailored advice about finding grey literature for your research topic. The document below guides you through the general process and presents several strategies.
For systematic and scoping reviews, a grey literature search may be mandatory or strongly recommended. For instance, Cochrane's MECIR standards recommend authors: "Search relevant grey literature sources such as reports, dissertations, theses, databases and databases of conference abstracts. Searches for studies should be as extensive as possible in order to reduce the risk of publication bias and to identify as much relevant evidence as possible."
Published journals may be susceptible to biases against reporting negative or neutral outcomes, a phenomenon known as "positive result bias." Researching grey literature or cross-referencing published studies with their grey literature counterparts (e.g. study protocols, clinical trials) can help combat various publication biases.
For other research projects, grey literature may be:
Grey literature consists of documents produced by government, academic, business or organizations "where publishing is not the primary activity of the producing body." (Greynet)
Examples include annual reports, conference proceedings, technical reports, theses, white papers, and even informal communication such as blogs, emails, or social media posts.