These may be searched using both subject and key word search techniques. Some periodical articles are available in full text in the online versions. Specialized indexes exist in several fields and you should be aware of them even if you don't have them in your own library. Several supplements were issued, and it is now being published annually with five-year cumulations. Also published by Wilson, its coverage begins in 1900.
Approach is by author and subject.
This is a good place to check for biographical information, too. The date to which coverage extends depends on the edition you have. It is more inclusive in coverage than Ottemiller. One problem you should be aware of with plays is that many are not published in collections at all but appear as separately printed pamphlets . These are often handled by companies like Samuel French or the Dramatists' Play Service, which not only sell the copies, but also sell the rights to perform the play and collect royalties on performances.