PHYSICAL HEALTH SCIENCES DATABASES:
SOCIAL HEALTH SCIENCES DATABASES:
NURSING AND NURSE ANESTHESIA DATABASES:
What is grey literature? According to the NLM, it is literature "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."
A.k.a. unpublished materials.
Here is a research guide full of up-to-date and rich information about how to find grey literature: