1. Bliss, J., Morrison, I. H., & Ogborn, J. (1988). A longitudinal study of dynamics concepts.International Journal of Science Education, 10, 99–110.
2. Brown, G., & Desforges, C. (1979).Piaget’s theory: A psychological critique. London: Routledge & Kegan Paul.
3. DES (1978a).Science progress report Assessment of Performance Unit, London: H.M.S.O.
4. DES (1978b).Science progress report, Appendix. List of science concepts and knowledge. Assessment of Performance Unit, London: H.M.S.O.
5. Repost to the DES and the Welsh Office on the 1981 survey. Assessment of Performance Unit;DES,1982