1. L.A. Albert, Proceedings of the Second International Symposium on Sustainable Agriculture, México, D.F., 1998 (in Spanish).
2. E.R. Bandala, J.A. Octaviano, V. Albiter, L.G. Torres, in: G.B. Wickramanayake, R.E. Hinchee (Eds.), Designing and Applying Treatment Technologies, Battelle Press, Columbus, OH, USA, 1998, p. 177.
3. Mexican Association of Chemical Industry (ANIQ), Annual Report of the Mexican Chemical Industry, México, D.F., 2000 (in Spanish).
4. National Institute of Statics, Geography and Informatics (INEGI), Monthly Industrial Report, México, D.F., 2000 (in Spanish).