1Poyhonen, Pentti (1963), A Tentative Model for the Volume of Trade Between Countries, Weltwirtschafliches Archive, Vol. 90, pp.93- 100.
2Helpman, E. (1987), Imperfect Competition and International Trade: Evidence from Fourteen Industrial Countries, Journal of Japanese and International Economy,MIT Press, Cambridge, MA.
3Deardorff, V. Alan(1995), Determinants of Bilateral Trade: Does Gravity Work in a Neoclassic World? National Bureau of Economic Research, Working Paper,5377.
4Frankel. Jeffrey. A, Regional Trading Blocs in the World Economic System, Institute for International Economics, Washington, DC.
5Garman George and Debora Gilliard (1999), Economic Integration in The Americas: 1975- 1992, The Journal of Applied Business Research, Vol. 14 Number 3.
6Wall J, Howard (1999), Using the Gravity Model to Estimate the Costs of Protection, January/February Review of Federal Bank of Saint Louis.
7Tamirisa, Natalia (1999) ,Exchange and Capital Control as Barriers to Trade, IMF Staff Papers.
8Sohn, Chon- Hyun,A Gravity Model Analysis of Korea's Trade Patterns and the Effects of a Regional Trading Arrangement, 2001,http://www.indo.com.