A guide to more than 23,000 national and international organizations, including: trade, business, and commercial; environmental and agricultural; legal, governmental, public administration, and military; engineering, technological, and natural and social sciences; educational; cultural; social welfare; health and medical; public affairs; fraternal, nationality, and ethnic; religious; veterans', hereditary, and patriotic; hobby and avocational; athletic and sports; labor unions, associations, and federations; chambers of commerce and trade and tourism; Greek letter and related organizations; and fan clubs.