3Grossman, G.M. and A.B. Krueger. Environmental Impacts of a North American Free Trade Agreement. In The Mexico-U.S.free trade agreement, ed. P. M. Gather. Cambridge, Massachusetts and London: MIT Press, 1993: 13-56.
4Antweiler Werner, Copeland Brian R. and Taylor M. Scott. Is Free Trade Good for the Environment? NBER Working Paper,1998, 6707.
5Antweiler Werner, Copeland Brian R. and Taylor M. Scott. Is Free Trade Good for the Environment? NBER Working Paper,2000.