1. Skolnick, P., and Daly, J. W., Science, 184, 175–177 (1974).
2. Segal, D. S., Kuczenski, R. J., and Mandell, A. J., Behav. Biol., 7, 75–81 (1972).
3. Huang, M., Ho, A. K. S., and Daly, J. W., Molec, Pharmac., 9, 711–717 (1973).
4. Kalisker, A., Rutledge, C. O., and Perkins, J. P., Molec. Pharmac., 9, 619–629 (1973).
5. Williams, B., and Pirch, J. H., Brain Res., 68, 227–234 (1974).