Cohen, H.L., Filipczak, J.A. and Biss, J.D.: An Initial Study of Contingencies Applicable to Special Education (Case 1 , U.S.A., Educational Facility Press, 1967.
2.
Cohen, H.L.: "Educational Therapy: The Design of Learning Environments." In: Research in Psychotherapy, Ed. J. M. Shlien, U.S.A., Amer. Psych. Assoc., 1968.
