Dramatists Play Service: Playfinder, allows searching by author, title, keyword, or gender, and number of cast members. Can purchase books or browse the catalog.
Inter-Play: an Online Index to Plays in Collections, Anthologies and Periodicals.
Keller, Dean H. Index to Plays in Periodicals. Metuchen, N.J.: Scarecrow, 1971.
Keller, Dean H. Index to Plays in Periodicals. Metuchen, N.J.: Scarecrow, 1979.
Keller, Dean H. Index to Plays in Periodicals, 1977-1987. Metuchen, N.J.: Scarecrow, 1990.
Samuel French: Theatre and plays bookshop.
Stratman, Carl J. Dramatic Play Lists, 1591-1963. New York : New York Public Library, 1966.