5Folland, S. ;Goodman, A. and Stano,M. The Economics of Health and Health Care. 2001 ,Prentice-Hall,Inc. Stigler, G. Theory of Price. 1987,New York: Macmillan.
6Stole, L.A. "Price Discrimination and Competition. " Handbook of Industrial Organization,Volume 3 ,edited by M. Armstmng;R. Porter and Elsevier B. V. ,Oxford,2007.
7Varian,H. R. " Price Discrimination. " Handbook of Industrial Organization, Volume 1, edited by R. Schmalensee; R.D. Willig and Elsevier B. V. ,Oxford,1989.