This continuing project includes plays published from the 16th to the early 20th centuries. Opera libretti and translations of plays written in languages other than German are also included. From 1961 through 1985, the set was produced in microcard format; from 1986 to date, it is in microfiche. CRL receives additional titles in this set periodically. At its completion, the set will include 12,000–15,000 titles.