@book{89818,
	author = {Keister, Donald L; Cregan, Perry B},
	title = {The rhizosphere and plant growth: papers presented at a symposium held May 8-11, 1989, at the Beltsville Agricultural Research Centre(BARC), Beltsville, Maryland},
	publisher = {Kluwer Academic Publishers},
	year = {1991},
	address = {Dordrecht}
}