Interlibrary Loan (ILL) is a system by which libraries share materials with each other.
If people need books not owned locally, their libraries will use WorldCat to find copies and borrow them from other libraries.
Notre Dame's ILL service is under "Services" on the library homepage. Follow that link to establish an account, after which placing a request is easy.
The service is free to individuals at Notre Dame.
These resources will help you find unpublished theses and dissertations, which present an author's research and findings as part of their degree candidacy or professional qualification.