2West, L. & Pines, A.(1985). Cognitive Structure and Conceptual Chang. Orlando, FL: Academic Press.
3Howe,A.C.(1996). Development of Science Concepts within a Vygotskian Framework. Science Education, 80(1),35-51.
4Wellman, H.M. & Gelnian, S.A.(1998).Knowledge Acquisition in Foundation Domains, in Kuhn D.& Siegler R.S (ed).Handbook of Child Psychology. New York: Wiley.5^th ed.
