Powers, Laura E. Ecological principles of agriculture / Laura E. Powers and Robert McSorley - New York : Delmar, c2000. - xi, 433 p. : ill. ; 24 cm. ISBN: 0766806537 LCCN: Subjects--Topical Terms: Agricultural ecology LC Class. No.: S589.7 / .P68 2000 Dewey Class. No.: 630.277 / P888e