Target your search using the following OER hubs and search widgets. Sure, you could just "Google it," but targeting your search will be most efficient.
Ask a librarian if you don't find what you are looking for. Below, are just a few of our "go-to" targeted resources.
A great overview of Open Textbook collections from https://t4lt.blogspot.com/ (3.5 min)
OER materials, such as open textbooks, are generally written by faculty or instructors of higher education.
As with any scholarship or textbooks, the quality of the work needs to be assessed, and peer review comments may be available.