1. Ballesteros, J., and A.J. Pérez. 1997.Sociedad y medio ambiente[Society and the environment]. Madrid: Trotta.
2. Barahona, E.A., R.M.R. Catalá, G.J.A. Chamizo, G.B. Rico, and A.V.A. Talanquer. 2006.Ciencias naturales: Quinto grado[Natural sciences: Fifth grade]. 3rd ed. México, DF: Secretaría de Educación Pública.
3. Environmental Education: A comparison between English and Mexican school children
4. Scale in children's experience with the environment