6Leibenstein. H. Economic backwardness and economic growth. Wiley, New York, 1957.
7Leibenstein. H.. The economic theory of fertility decline. Quarterly Journal of Economics.
8Becker. G. S. An economic analysis of fertility. In Demographic and Change in Developed Countries: A Conference of the Universities- National Bureau Committee for Economics. NBER, Princeton University Press, Princeton, New Jersey, 1960.
9Becker. G.S. Lewis. H.G. On interaction between quality and quantity of children. Journal of Political Economy 81 (1973 ,supplement).
