1. Huxley, J., Mayr, E., and Osmond, H., Nature, 204, 220 (1964).
2. Baldessarini, R. J., and Snyder, S. H., Nature, 206, 1111 (1965).
3. Payne, R. W., Matussek, P., and George, E. I., J. Ment. Sci., 104 (1959).
4. Rodnick, E. H., and Garmezy, N., in Nebraska Symposium on Motivation, edit. by Jones M. R. (University of Nebraska Press, 1957).
5. Hamilton, V., and Salmon, P., J. Ment. Sci., 108 (1962).