1. H. E. Himwich, J. Am. Med. Assoc. 163: 545 (1975).
2. A. Goldstein and B. A. Judson, Science 172: 290 (1971).
3. H. Kalant and P. E. Dews, in: Experimental Approaches to the Study of Drug Dependence ( H. Kalant and R. D. Hawkins), pp. 100 - 134, University of Toronto Press, Toronto (1969).
4. J. D. Sinclair, J. Adkins, and S. Walker, Nature (Lond.) 246: 425 (1973).
5. R. Galfant and Z. Amit, Nature (Lond.) 259: 415 (1976).