1. Brainerd, C. J. (1987). Learning research and Piagetian theory. In I. Siegel, & C. J. Brainerd (Eds.),Alternatives to Piaget. Critical essays on the theory (pp. 69–109). New York: Academic Press.
2. Bruner, J. S. (1966). On the conservation of liquids. In J. S. Bruner, R. R. Olver, & P. M. Greenfield (Eds.),Studies in cognitive growth (pp. 183–207). New York: Wiley.
3. Donaldson, M. (1978).Children's minds. London: Fontana.
4. Elbers, E. (1986). Interaction and instruction in the conservation experiment.European Journal of Psychology of Education 1, 77–89.
5. Elbers, E. (1991a). The development of competence and its social context.Educational Psychology Review, 3, 73–94.