7Anderson, J. E.. A Theoretical Foundation of the Gravity Model. American Economic Review, 1979, 69, 106-116.
8Bergstrand, J. H. . The Gravity Equation in International Trade : Some Microeconomic Foundations and Empirical Evidence. The Review of Economics and Statistics, 1985, 67,474 -481.
9Brada, Josef C. and Mendez, Jose A( 1985 ) Economic Integration among Developed, Developing and Centrally Planned Economies: A Comparative Analysis. The review of Economics Statistics 67, 549 - 556.
10Linnemann, H.. An Econometric Study of International Trade Flows. Amsterdam: North - Holland Publishing Company, 1966.
