Grey literature is information produced outside traditional academic or commercial publishing avenues. It exists in a variety of formats, including blogs, government websites and reports, interviews, newsletters, dissertations, statistical reports, white papers, and so on.
NGO Search is a custom Google search that searches across thousands of non-governmental organizations (NGO). NGO Search is project of the Government Documents Roundtable (GODORT) of the American Library Association (ALA).
Use Google's advanced search functions to find grey literature.
Try the site limiter to search within specific domains. For example, search site: .gov with a keyword to locate grey literature on government websites.
Use the file type limiter to search for certain file formats, like .pdf or .xlsx. For example, search filetype: .pdf with a keyword to locate reports and other sources published as PDFs.