WorldCat is a world-wide catalog of books. It's possible to request books from other libraries (beyond Mobius libraries) through WorldCat. WorldCat functions in the same way as the WU catalog; you may search by keyword or subject.
Just as with the WU catalog, the subject headings are listed as links at the bottom of the record. I highly recommend exploring WorldCat to see what other sources are out there.
We have access to two WorldCat interfaces. One is free, one is subscription. I prefer the subscription version. Links are below: