Systematic Literature Review: Grey Literature

These are good places to search for grey literature:

World Health Organization International Clinical Trials Registry Platform (ICTRP; link opens in a new window): a searchable registry of clinical trials from all around the world
Sources of grey literature (link opens in new window) focused on research and policy documents from countries in the Global South
ScanMedicine (link opens in a new window): 11 clinical trial databases worldwide can be searched simultaneously.
UK Clinical Trials Gateway (link opens in a new window): a searchable database of non-commercial clinical trials
ClinicalTrials.gov (link opens in a new window): a registry of clinical trials in the US
Trials Register of Promoting Health Interventions (TRoPHI; link opens in a new window): a searchable database containing details of over 7750 clinical trials focusing on public health.
NICE Local Practice Case Studies (link opens in a new window): a collection of over 500 working examples of quality improvement in health and social care services
Social Care Online (link opens in a new window): grey literature for social care and social work
Google Scholar (link opens in a new window): Google Scholar is a freely accessible web search engine that indexes scholarly literature's full text or metadata across various publishing formats and disciplines, facilitating the easy discovery of academic resources.
Semantic Scholar (link opens in a new window): Semantic Scholar is an AI-powered research tool developed by the Allen Institute for AI, designed to help scholars quickly discover relevant information by navigating the vast amount of scientific research available online.
Core Repository (link opens in a new window): A core repository is a centralized digital archive that collects, preserves, and provides access to research outputs, scholarly publications, and data sets to support the dissemination and long-term storage of academic work.
The lens is a tool to link open knowledge artifacts and metadata with tools to inform effective, efficient, and equitable problem-solving.

Your systematic review will likely need to include a search of grey literature and peer-reviewed journal articles found through database searching. Grey literature includes unpublished theses, conference proceedings, government reports, unpublished trial data, and more. Leaving out grey literature can run the risk of biasing your results, as doctor and epidemiologist Ben Goldacre explains in the video below.

Searching for gray literature can be challenging. Most sources of grey literature cannot be searched with complex Boolean searches the way you would search a database. The CADTH tool (link opens in a new window) for searching grey literature can help. There is also a useful journal article with supplementary files giving step-by-step instructions on searching different sources of information for grey literature: Godin, K., Stapleton, J., Kirkpatrick, S.I., et al. Applying systematic review search methods to the grey literature: a case study examining guidelines for school-based breakfast programs in Canada. Syst Rev 4, 138 (2015) (link opens in a new window).

The NHS Learning Academy has created a guide to grey literature (link opens in a new tab), explaining why and how to use grey literature and some sources.