Keller, Fred S. 1899-1996. Learning: reinforcement theory [by] Fred S. Keller. - 2d ed. - New York, Random House [1969] - 82 p. illus. 19 cm. LCCN: 74081165 LC Class. No.: LB1051 .K36 1969 / .K36 1969 Dewey Class. No.: 153.1/5