7Caselli, Francesco and Wilbur John Colemanll. "The World Technology Frontier", NBER Working Paper No.7 904,2000.
8Douglass North, Structure and Change in Economic History, New Haven: Yale Universit Press, 1983.
9Krugman,P., 1979. A Model of Innovation, Technology Transfer and the World Distribution of Income. Journal of Political Economy 87(2), April,pp. 253-266.
10Grossanan, G.M., and Helprnan, E., 1991a. Quality Laders and Product Cycles, Qurtedy Journal of Economics,May, pp.557 - 586.