Sylvester-Bradley, P. C. The species concept in paleontology : a symposium - London : The Systematics Association, 1956 - 145 p. : ilus. - The Systematics Association. Publication ; 2 . - The Systematics Association. Publication ; 2 . LCCN: 58629 Subjects--Topical Terms: Especies.Paleontología. Dewey Class. No.: 560 / S9