Gruber, K., Cloyd, I., Koek, K. E., Boyles, S. M., & Paré, M. A. (1985). Encyclopedia of associations: A guide to approximately 20,000 national and international organizations including: trade, business, and commercial ; agricultural and commodity ; legal, governmental, public administration, and military ; scientific, engineering, and technical ; educational ; cultural ; social welfare ; health and medical ; public affairs ; fraternal, foreign interest, nationality, and ethnic ; religious ; veteran, hereditary, and patriotic ; hobby and avocational ; athletic and sports ; labor unions, associations, and federations ; chambers of commerce ; and Greek letter and related organizations (20th edition.). Detroit, MI: Gale Research Co..

Gruber, Katherine., Iris Cloyd, Karin E. Koek, Susan M. Boyles, and Michael A. Paré. Encyclopedia of Associations: A Guide to Approximately 20,000 National and International Organizations Including: Trade, Business, and Commercial ; Agricultural and Commodity ; Legal, Governmental, Public Administration, and Military ; Scientific, Engineering, and Technical ; Educational ; Cultural ; Social Welfare ; Health and Medical ; Public Affairs ; Fraternal, Foreign Interest, Nationality, and Ethnic ; Religious ; Veteran, Hereditary, and Patriotic ; Hobby and Avocational ; Athletic and Sports ; Labor Unions, Associations, and Federations ; Chambers of Commerce ; and Greek Letter and Related Organizations. 20th edition. Detroit, MI: Gale Research Co., 1985.

Gruber, Katherine., et al. Encyclopedia of Associations: A Guide to Approximately 20,000 National and International Organizations Including: Trade, Business, and Commercial ; Agricultural and Commodity ; Legal, Governmental, Public Administration, and Military ; Scientific, Engineering, and Technical ; Educational ; Cultural ; Social Welfare ; Health and Medical ; Public Affairs ; Fraternal, Foreign Interest, Nationality, and Ethnic ; Religious ; Veteran, Hereditary, and Patriotic ; Hobby and Avocational ; Athletic and Sports ; Labor Unions, Associations, and Federations ; Chambers of Commerce ; and Greek Letter and Related Organizations. 20th edition. Detroit, MI: Gale Research Co., 1985.