OneSearch
OneSearch includes online articles from dictionaries and encyclopedias. Search for your topic, then limit your results to these articles by using the "Refine my results" list on the left:
Credo searches encyclopedias, dictionaries and other reference sources.
Cambridge Histories of Theatre
Browsing the Reference Books
Reference books are located on the first floor of the library, with the call numbers:
Theatre Encyclopedias: A Sample