1. Bindra, D., Motivation, a Systematic Reinterpretation, chapter 5 (Ronald, New York, 1959).
2. Cofer, C. N., and Appley, M. H., Motivation: Theory and Research, chapter 11 (Wiley, New York, 1964).
3. Kimble, G. A., Hilgard and Marquis' Conditioning and Learning, chapter 9 (Appleton-Century-Crofts, New York, 1961).
4. Valenstein, E. S., Hodos, W., and Stein, L., Amer. J. Psychol., 74, 125 (1961).
5. Bindra, D., and Palfai, T., J. Comp. Physiol. Psychol., 63, 288 (1967).