This resource should help you read and write about plays.
FINDING AIDS GUIDE
Items are edited together into single volumes.
Subject-specific dictionaries exist for a variety of topics.
A book containing one or more alphabetical lists of the inhabitants of any locality, with their addresses and occupations; also a similar compilation dealing with the members of a particular profession, trade, or association, for example a Clerical or Medical Dictionary, etc. Infomine is good for subject specific directories.
Archives and Manuscripts
Patent and Statistical Databases
Technical Surveys and Reports
Thesauri -- Classified list of terms or keywords
Art and Architecture
Cultures, Anthropology, and Sociology
Law and Politics
Science and Mathematics
National Union Catalog is an example. Another example is OCLC Worldcat.