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WorldCat is a catalog of multiple libraries, not just the UMD Libraries. The default search is what is owned by UMD Libraries. Since it is not possible to go to the stacks to look for a book, books have to be requested for curbside pickup. Click on the request button in the catalog record. After the book is available, you will be asked to schedule curbside pickup.
Use "best match" on left to see what might be owned by other libraries on a topic. Books can be borrowed from other libraries using the "Request through Interlibrary Loan" button. Curbside pickup operates here as well,
The UMD Libraries own many e-books in addition to print books. Access requires UMD ID and password. A search in WorldCat can be limited to e-books using the advanced search. Note that e-books not owned by UMD can be requested through interlibrary loan but without guarantee of obtaining.
Internet Archive Open Library" Open Library is an open, editable library catalog, building towards a web page for every book ever published." Complete digital copies of many books are included. Access is freely available though requires an account, easily created.
Google Books has digitized millions of titles. Books still in copyright (generally published after about 1925) are only available in part. Many books out of copyright are available in their entirety, which makes this a rich repository of primary sources.