1. Baumol, W.J. and Bowen, W. G. (1966).Performing arts: The economic dilemma. New York: Twentieth Century Fund.
2. Bradford, D.F. (1969). Balance on unbalanced growth.Zeitschrift für Nationalökonomie 29: 291?304.
3. Organization for Economic Cooperation and Development (OECD). (1990).Health care systems in transition: The search for efficiency. Paris.
4. United Nations Educational, Scientific and Cultural Organization (UNESCO),Statistical year-book. Paris. Various issues.
5. U.S. Department of Commerce, Bureau of the Census.Statistical Abstract of the United States. Washington, DC: U.S. Government Printing Office. Various years.