8Bergstrand , J. H.. The Gravity Equation in International Trade : Some Microeconomic Foundations and Empirical Evidence. Review of Economics and Statistics, 1985,67 : 474 -481.
9Poyhonen, P.. A Tentative Model For the Flows of Trade Between Countries. Weltwirtschat f tliches A rchiv 1963,90 ( 1 ) :93-99.
10Tinbergen, J.. Shaping the world Economy: suggestion for an International Economic Policy. New York:The Twentieth Century Fund, 1962.
