The World Atlas of Language Structures (WALS) is a large database of structural (phonological, grammatical, lexical) properties of languages gathered from descriptive materials (such as reference grammars).
DiscoverUR: Use filters to narrow to linguistics-related items.
Remember, your sources need to be peer-reviewed and produced by a scholarly publisher. Materials created by native speakers can be given special consideration.
Your sources should also have:
If you come across items on endangered languages that would be helpful for your research and that UR does not own, please let me know and I will purchase these items using the funds I have for Linguistics collection development.