1. Van der Lee, S., and Boot, L. M., Acta Physiol. Pharmacol. Neerl., 5, 213 (1956).
2. Whitten, W. K., J. Endocrinol., 18, 102 (1959).
3. Whitten, W. K., Science, 16, 584 (1968).
4. Parkes, A. S., and Bruce, H. M., J. Reprod. Fertil., 4, 303 (1962).
5. Thiessen, D., Texas Rep. Biol. Med., 22, 266 (1964); Leiderman, P. H., and Shapiro, D., Psychobiological Approaches to Social Behavior (Stanford University Press, 1964).