Readers’ Guide was one of the most heavily used printed periodical indexes of the 20th century. Note the broad subject categories, the many “see also” references, and the abbreviated nature of the citations. Its content for 1890 through 1980 is now available online as the Readers’ Guide Retrospective database.

Compact disc format offered not only efficient data storage – these two discs contain the equivalent of 64 printed SSCI volumes – but local distribution, eliminating the need for “live” (and expensive) network connections to centralized databases. Periodical databases on CD-ROM were made available for patrons to use without charge, and simplified interfaces freed them to search on their own.