Selected articles in library's 500+ historical and genealogical periodicals have been indexed according to author, title, and subject in the library catalog. Library visitors should search both the online catalog and the old card catalog for articles located in "Periodicals" and "Vertical File." A periodical index is also available as a separate card file in the library. While this index is not current, it is a useful source of information for topical research. The Periodical Source List Index (PERSI) is a helpful resource for locating articles of genealogical interest. PERSI is available in the library through an online subscription to HeritageQuest Online.