@book{72023,
	author = {Verma, P.S. and Agarwall, V.K.},
	title = {Principles of ecology = environmental biology/},
	publisher = {S. Chand, },
	year = {1989.},
	address = {New Delhi:},
	edition = {4th ed.},
	note = {[Includes glossary, bibliographies and index]}
}