Books are an excellent resource for theatre history, commentary on plays and the theatre, design, production, and more. All books in the library's print and online collections can be searched using the library's main Discovery search box. This search also includes plays, videos, music and full text articles. You can choose a tab to limit in advance, or use the limits on the left after beginning a search.
Discovery also offers the option to expand your search to libraries worldwide and then links to "interlibrary loan". Most books arrive in 1 to 3 weeks and can be picked up at the main library desk.
Reference books can also be useful sources, but may not appear in a search for a specific topic. Some examples included here are encyclopedias of theatre and literature. The Oxford Reference Online search searches within several such online reference books.