1. Field, D. Long-term effects of conservation training with educationally subnormal chüdren. Journal of Special Education, 1974, 8, 237–245.
2. Field, D. The importance of the verbal content in the training of Piagetian conservation skills. Child Development, 1977, 48, 1583–1592.
3. Field, D. How children in ESN schools in London learn conservation sküls. In G. L. Lubin, M. K. Poulsen, J. F. Magary, and M. Soto-McMister (Eds.). Piagetian Theory and its Implications for the Helping Professions, Proceedings of the Seventh Inter-disciplinary Conference (Vol. 2). Los Angeles: University of Southern California Press, 1978.
4. Piaget, J. The Child’s Conception of Number. London: Routledge and Kegan Paul, 1952.
5. B. Inhelder, H. Sinclair, and M. Bovet. Learning and the Development of Cognition. London: Routledge and Kegan Paul, 1974.