Solow R. Techenical change and the aggregate production function. Rev Econ Stat 1957 (aug)? Rosenberg N. Inside the balck box: technology and economics. New York: Cambridge University, 1982. OECD. Main science and technology indicators. Paris: OECD, 1996. Okun AM. Equality and efficiency: the big tradeoff. Washington: The Brookings Institution, 1975:1. OECD. Manual de Frascati. Paris: OECD, 1993:47-66. Nicholson W. Microeconomic theory: basic principles and extensions. 3 ed. Chicago: Dryden Press, 1985:706-9.