1. Farmighetti R, editor. The world almanac. Mahwah, NJ World Almanac Books, 1996.
2. United States Department of Commerce, Statistical Abstract of the United States 1995: The national data book. 115th ed. US Department of Commerce, 1995.
3. National Center for Health Statistics. Health, United States, 1994. Hyatsville, MD: Public Health Service, 1995.
4. Britannica Online, United States of America: Government, Chicago, IL: Encyclopedia Brittanica Inc. version 96(2), 1996.
5. Jonas, S. An introduction to the US healthcare system. New York: Springer, 1992.