1. T. S. Kuhn,The Structure of Scientific Revolutions, University of Chicago Press, 1970.
2. J. Piaget, Scientific American, November 1953, page 74;
3. March 1957, page 46;
4. J. Piaget and B. Inhelder,Child's Concept of Space, Routledge and Paul, London, 1956.
5. J. Piaget,Proceedingsof the Symposium in Honor of the Fiftieth Anniversary of the Niels Bohr Institute, Copenhagen, 1970;