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Buxbaum, E. (1974) Play and Development: Symposium with Contributions by Jean Piaget, Peter H. Wolff, René A. Spitz, Konrad Lorenz, Lois Barclay Murphy, Erik H. Erikson. Edited by Maria W. Piers. New York: W. W. Norton & Co., Inc., 1972. 176 pp.. Psychoanalytic Quarterly 43:311-315