There are several books that are referred to as "the Green Book." Here are some that are relevant to the legal field:
House Ways and Means Committee
The House Ways and Means Committee Green Book (aka Background Material and Data on Programs within the Jurisdiction of the Committee on Ways and Means) provides program descriptions and historical data on a wide variety of social and economic topics, including Social Security, employment, earnings, welfare, child support, health insurance, the elderly, families with children, poverty and taxation. It has become a standard reference work for those interested in the direction of social policy in the United States. It is compiled by the staff of the Committee on Ways and Means of the U.S. House of Representatives. The Green Book is available for 1996, 1998, 2000 and 2004.
This manual by the National Housing Law Project includes new policies, emergent case law, and regulatory changes that shape the legal framework for cases that impact HUD tenants. The Green Book also contains unpublished court decisions, hard-to-find memos, and legal theories and strategies, providing a comprehensive treatise on evictions, subsidy terminations, affordable housing preservation and much more.
The ICRG set, conveniently organized into global regions, is a source of foundational and comprehensive citation standards for scholars working with all types of international and foreign materials. It presents each citation standard in the context of that country or organization's history and legal institutions. It is also a general resource of basic legal background on international organizations and countries that would otherwise be difficult to research. It can be used as a companion to The Bluebook, whose coverage of international sources is necessarily limited.