This comprehensive yet concise annotated reference source catalogs the important series, periodicals and reference tools published by U.S. government agencies. Over the years, the index section of the Guide to U.S. Government Publications has expanded to include more than 42,500 entries. Agencies and titles are indexed, followed by a keyword-in-title index for quick and easy referencing. No other single resource provides historical and current information on U.S. government publications in one place. Guide to U.S. Government Publications, also includes agency class chronologies providing complete histories of current class number assignments allowing researchers to track changes in older serials. Forty years since its inception, the Guide to U.S. Government Publications has become a standard reference source in federal document collections, featuring: SuDocs class number, depository item numbers, title, beginning and closing dates, frequency, select annotations, title changes, class number references to earlier and later classes, and ISSN for periodicals. Complete listing of the Superintendent of Documents Classifications Scheme outlining the basics of the U.S. government's complex document system. Alphabetical indexes by agency and title. 500 page keyword title index.