There are a few different places you can look for books:
1. WashU's Classic Catalog has information about both print and online books held by all of the WashU Libraries. You can use the search tool below or visit this page.
2. You can search for books not held by WashU in MOBIUS, a partnership of nearby libraries (mostly in Missouri). To request a book, click on 
Request and select your library from the drop-down. Items usually arrive in 3-7 days.
3. If an item is not found in the Classic Catalog or in MOBIUS, you can search libraries worldwide using WorldCat and submit an Interlibrary Loan (ILL) request. Items usually arrive in 1-2 weeks.
MOBIUS is a partnership of libraries that provides access to shared resources. There are 77 members and 226 physical branches, which include both academic and public libraries. Most are in Missouri, but there are also branches in Iowa, Illinois, Oklahoma, Kansas, and more.
If your desired book is not held by WashU, you can request it from another MOBIUS library that holds it. For more information about submitting a MOBIUS request, visit this page.
WorldCat is the world's largest network of library services. It allows you to search the catalogs of over 10,000 libraries worldwide.
If you cannot find your book in WashU's catalog or on MOBIUS, you can submit an ILL request to a library on WorldCat. For more information about submitting an ILL request, visit this page.
At WUSTL, and at many academic libraries in the United States, we use an organization system developed by the Library of Congress. This system works to organize materials by subject.
For more information on this organization schema, please see the Library of Congress Classification Outline.
Here is a hypothetical shelf of books with the call numbers explained:
