Belleza vs contaminación (videos you tobe)

http://www.youtube.com/watch?v=ey2UqUBqqO4
http://www.youtube.com/watch?v=Azi3tRRpTKo&feature=related
http://www.youtube.com/watch?v=634hY7aLUbo&feature=related
http://www.youtube.com/watch?v=W9PnWlTBSBU
http://www.youtube.com/watch?v=rCx4GE7PAYU
http://www.youtube.com/watch?v=_7KuFVg6RXc

Biblioteca virtual:
http://www.bibliotecasvirtuales.com/biblioteca/articulos/abrahambastidaaguilar/otracontaminacion.asp
http://portal.bibliotecasvirtuales.com/foros/la-contaminacion
http://portal.bibliotecasvirtuales.com/foros/evolucion-y-naturaleza