3Caves, D.W., Christensen, L.R., & Diewert, W. E., Multilateral comparisons of output, input and productivity using superlative index numbers. Economic Journal, 92,1982, pp.73-86.
4Cohen W, and Levinthal D. Innovation and learning, the two faces of R&D. Economic Journal, 99,1989,pp.569-596.
5Fare,R. ,Grosskopf, S. ,& Lovell,C.A.K., Production Frontiers. Cambridge: Cambridge University Press, 1994.
6Greene. W., Econometric(Fourth Edition). Prentice Hall Press, 2000, pp557-589.