References
- Bitterman , M. E. , Fedderson , W. E. and Tyler , D. W. 1953 . Secondary reinforcement and the discrimination hypothesis . Amer. J. Psychol. , 66 : 456 – 464 .
- Kimble , G. A. 1961 . Hilgard and Marquis' Conditioning and Learning 320 – 323 . New York : Appleton-Century-Crofts. .