1. Aries, P. (1965).Centuries of Childhood, Vintage Books, New York.
2. Bruner, J. (1966).Studies in Cognitive Growth, Wiley, New York, Chapters 11, 12, and 13.
3. Hudson, L. (1966).Contrary Imaginations, Schocken Books, New York.
4. Keniston, K. (1970). A new stage of life.American Scholar 39: 631?654.
5. Piaget, J., and Inhelder, B. (1958).The Growth of Logical Thinking from Childhood to Adolescence, Basic Books, New York.