8BECKER G. S. , BARRO R. J. 1988. A reformulation of the economic theory of fertility [ J ]. Quarterly Journal of Economics, 103 (1) : 1 - 25.
9SILBER, J. 1989. Factor components, population subgroups, and the computation of the Gini index of inequality [ J ]. Review of Economic and Statistics, 71 (1): 107-115.