@book{4212,
	author = {Ehrlich, Paul R. and Ehrlich, Anne H.,},
	title = {Population resources environment :},
	publisher = {W. H. Freeman ,},
	year = {1970.},
	series = {A Series of books in biology},
	address = {San Francisco :},
	note = {Third ed. published in 1977 under title: Ecoscience.}
}