7Tinbergen,J.. Shaping the World Economy: Suggestions for an International Economic Policy [Z] .New York: The Twentieth Century Fund,1962
8Poyhonen, P..A Tentative Model for the Flows of Trade Between Countries [J] .Wehwirtschatftliches Archiv90, (1) ,1963
9Anderson,N.D.and R.S. Obutelewicz .A Cross-Sectional Study of EEC Trade with the Association of African Countries [J] .Review of Economic and Statistics,1976
10Bergstrand,Jeffery,H.. The Gravity Equation in International Trade: Some Microeconomic Foundation and Empirical Evidence [J] .The Review of Economics and Statistics, (20) ,1985
