When looking for grey literature you may want to explore organisations relevant to your research area in order to find unpublished material.
These groups might include:
Scopus allows you to analyse search results and identify affiliated organisations (e.g. universities, research centres) to explore further
Scopus results analyzer
You can choose a date range when analysing the results (top right).
This will show the top affiliations from your search results, based on frequency; they may have websites to explore
Web of Science also allows you to analyse your search results to identify potentially relevant organisations.
Web of Science results analysis
'Specify all databases, registers, websites, organisations, reference lists, and other sources searched or consulted to identify studies. Specify the date when each source was last searched or consulted' - PRISMA Explanation and Elaboration, p. 5
Organisations that could be valuable sources of grey literature, playing a role in producing, collecting, evaluating and/or making this more accessible: