International catalog containing over 95 million records of books and other materials held in libraries worldwide. Titles unavailable elsewhere can be requested here.
The Center for Research Libraries is in Chicago, but it will send MU Libraries patrons its primary sources on very generous interlibrary loan terms. The link goes to CRL's Topic Guides, which are excellent overviews of primary sources available for loan.
MU is a partner institution, so you can log in, which will allow you to create personal collections of books. You can search the full text even of books that cannot be downloaded.