1. Ayllon, T., and Haughton, E., 1964, Modification of symptomatic verbal behaviour of mental patients, Beh. Res. & Ther., 2:87–97.
2. Barton, E.S., 1972, Operant conditioning of social speech in the severely subnormal and the use of different reinforces, Brit. J. Soc. & Clin. Psychol., 11:387–396.
3. Barton, E.S., 1973, Operant conditioning of appropriate and inappropriate speech in the profoundly retarded, J. Ment. Def. Res., 17:183–191.
4. Carlson, C., Hersen, M., and Eisler, R., 1972, Token economy programmes in the treatment of hospitalised adult schizophrenics, J. Nerv. & Ment. Dis. 115:192–204.
5. Fraser, D., 1976, An integrated system of behavioural assessment, Beh. Mod., 9:17–30.