Grey literature databases identify resources that are key to research and scholarship. Many are open resources that go through a quality control process before they are published. Note the contributions of government databases for articles, maps, and data.
Definitions are scholarly dictionaries, encyclopedias and handbooks that help define terms and provide additional context.
The Encyclopedia of Earth (current, open)
Geology Dictionary (current, Geology.com)
Divisions of Geologic Time (Geology.com)
Geologic Time Scale 2020 (2020)
Occupational Health and Safety information is essential to dealing with injuries, accidents, government and regulatory information.
Theses and Dissertations are important unpublished resources granted and retained by universities as capstone projects, these, and dissertations.
Open Education Resources (OERs) are digital ebooks and learning objects that can be used as open textbooks on a wide variety of general and disciplinary subjects.