For background information, use the Resource Type > Reference Entries limit. Other helpful limiters:
- include or exclude other Resource Type limits
- Availability>Peer-reviewed Journals
- Creation Date
Search with the publication(s) that laid out the theory to see who and how it's been used.
Some of the books on your syllabus are available. Ebooks may be limited to one simultaneous user, so if you can't access it, try again.