The Fourth International Conference on Grey Literature (GL '99) in Washington, DC, in October 1999 defined grey literature as follows: "That which is produced on all levels of government, academics, business and industry in print and electronic formats, but which is not controlled by commercial publishers." - New York Academy of Medicine
From The Institute of Medicine:
Take action to address potentially biased reporting of research results.
Search grey literature databases, clinical trial registries, and other sources of unpublished information about studies
Grey Lit Sources: