"That which is produced on all levels of govenment, academics, business and industry in print and electronic formats, but which is not controlled by commercial publishers." (Fourth International conference on Grey Literature, Washington D.C., October 1999)
Examples of grey literature may include:
Market research reports
Newsletters and/or bulletins
Dissertations & Theses
Why grey literature can be a good source:
Your research may be a topic that governments spend time and money understanding, such as land management or infrastructure.
Your research may want to consider the point of view of local, state, or national governments.
The grey literature may have a more practical rather than academic viewpoint.
The publication may be sharply focused on a local issue you want to study, such as a dissertation about the ecosystem of a local park.
The grey literature may be the only timely information available.