5Colin Clark, The Conditions of Economic Progress, London: Macmillian, 1940.
6Robert Summers, Services in the International Economy, in Robert P. Inman, Managing the Service Economy : Prospects and Problems, New York: Cambrudge University Press,1985, pp27 - 48.
7Rodney E. Falvey and Norman Gemmell, Are Services Income-elastic? Some New Evidence, Raview of Income and Wealth, Series 42, Number 3, September 1996.
8Thomas M. Stanback, Jr. , Perter J. Bearse, Thierry J. Noyelle and Robert A. Karasek, Service: The New Economy, New Jersey: Allanheid, Osmun & Co. Publishers, Inc, 1981, pp.49 - 65.
9Joseph F. Francois, Producer Services, Scale, and the Division of Labor, Oxford Economic Papers, Oct 1990 ,42,4.
10Harry I. Greenfield, Manpower and the Growth of Producer Services, New York: Columbia University Press, 1966, pp.37 - 47.
