Book excerpt: This unique guide helps to answer two important questions for researchers planning to use government information sources. First, over which aspects of individual, organizational, national, and international affairs does the U.S. government exert authority or influence? Second, which units of the federal government are empowered to probe and pursue these matters? The contents and format of Jerrold Zwirn's new research aid offer a concise, yet complete, overview of contemporary public affairs and governmental policy agents. In this guide, Zwirn provides the researcher with comprehensive coverage of the issues and topics addressed by all key units of the national executive and legislative branches. He identifies each entity that exercises jurisdiction over a specific subject in order to facilitate optimum access to the entire domain of federal business and the corresponding sources of federal information. By using a tandem subject and author approach, the guide enables users to focus quickly on functions assigned or implied by a legal mandate. This scheme records and reveals the relationships between formal powers and official authors. Zwirn's immediate aim is to assist those who plan to enter and explore the federal information thicket. His ultimate goal is to devise a framework that can be adapted to the dynamic character of national governance and its information output. Access to U.S. Government Information will be an essential tool for political scientists, legal researchers, librarians, and anyone interested in public policy, policymakers, and the links between them.