Library cooperation on regional and statewide levels has helped to expand significantly the collections of individual research libraries through cooperative purchasing policies, cataloging networks, union lists, interlibrary loan services and other means. However, access to the contents of these materials is also essential if this vast body of information is to be utilized fully. Books on specific topics can be found with relative ease by searching library subject catalogs, printed bibliographies, and specialized data bases. On the other hand, the wealth of information that appears regularly in periodical literature is all but lost unless it is adequately indexed.