REFERENCES
- Beveridge , M. and Hurrell , P. 1980 . Teachers responses to severely mentally handicapped children's initiations in the classroom . 21 : 175 – 181 .
- Merrett , F.E. and Musgrove , W.J. 1982 . The hierarchy of reinforcement: mainspring of the behavioural approach to teaching and learning . 2 : 301 – 312 .