@book{201033,
	author = {Enger, Eldon D. and Smith, Bradley F.},
	title = {Ciencia ambiental},
	publisher = {McGraw-Hill},
	year = {c2006.},
	address = {México},
	edition = {10th ed.},
	note = {Includes index.},
	url = {http://www.loc.gov/catdir/toc/ecip0422/2004019843.html}
}