1. Campbell, B. A., & Sheffield, F. D. Relation of random activity to food deprivation. J. comp. physiol. Psyckol., 1953, 46, 320–322.
2. Gibson, W. E., Reid, L. D., Sakai, M., & Porter, P. B. Intracranial reinforcement compared with sugar-water reinforcement. Science, 1965, 148, 1357–1359.
3. Kimble, G. A. Hilgard and Marquis’ conditioning and learning. New York: Appleton-Century-Crofts, 1961. P. 263.
4. Lindquist, E. F. Design and analysis of experiments in psychology and education. Boston: Houghton Mifflin, 1953.
5. Morgan, C. T. Physiological psychology. New York: McGraw-Hill, 1965. P. 329.