Bellak, L. 1., Cattell, R. B. 1., Klein, G. S. 1., McClelland, D. C. 1., Mead, M. 1., & McCary, J. L. 1. (1959). Psychology of personality: Six modern approaches (First Evergreen edition.). New York: Grove Press, Inc.

Bellak, Leopold 1916-, Raymond Bernard 1905-1998 Cattell, George Stuart 1917-1971 Klein, David Clarence 1917-1998 McClelland, Margaret 1901-1978 Mead, and James Leslie 1919-1978 McCary. Psychology of Personality: Six Modern Approaches. First Evergreen edition. New York: Grove Press, Inc, 1959.

Bellak, Leopold 1916-, et al. Psychology of Personality: Six Modern Approaches. First Evergreen edition. New York: Grove Press, Inc, 1959.