"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.“ [ Fourth International Conference Grey Literature 1999]
In general, grey literature publications are non-conventional and sometimes ephemeral publications. Given the wide range of sources that encompass Grey Literature, there is no definitive list.
Examples of Grey Literature Sources
[Image from: http://guides.library.uq.edu.au/how-to-find/grey-literature]