Grey literature is “information produced by all levels of government, academics, business and industry in electronic and print formats not controlled by commercial publishing”. (GreyNet)

Grey literature includes

Including grey literature in your search strategy will help you discover

• newly disseminated findings
• information about less successful studies that have not been included in published studies
• reports and statistics that are not available in traditional published sources

This will help you

• include some alternative perspectives
• offset possible bias in published results
• include more local information
• fill in research gaps

Bonato, S. (2018). Searching the Grey Literature: A handbook for searching reports, working papers, and other unpublished research. Lanham, Maryland: Rowman & Littlefield Publishing.

Pappas, C., & Williams, I. (2011). Grey Literature: Its Emerging Importance. Journal of Hospital Librarianship, 11(3), 228-234. doi:10.1080/15323269.2011.587100

Paez, A. (2017). Gray literature: An important resource in systematic reviews. Journal of Evidence-Based Medicine, 10(3), 233-240. doi:10.1111/jebm.12266

Mahood, Q., Van Eerd, D., & Irvin, E. (2013). Searching for grey literature for systematic reviews: challenges and benefits. Research Synthesis Methods, 5(3), 221-234. doi:10.1002/jrsm.1106

Lawrence, A. (2012). Electronic documents in a print world: Grey literature and the internet. Media International Australia 143 doi: 10.4225/50/5580B0D739AF5