8Inmaculada,M.Gravity Model:An Application to Trade BetweenRegional Blocs[J].Atlantic Economic Journal,2003(31):174-187.
9Lee,J. and I.Park.Free Trade Areas in East Asia: Discriminatoryor Non Discriminatory [J]. World Economy,2005(28):21-48.
10Peter A. G. van Bergeijk, Steven Brakman.The Gravity Model inInternational Trade. Advances and Applications [J]. American E-conomic Review,2011(19):979-981.