1Hart, K.M.(1981).Children's Understanding of Mathematics:11-16.Oxford London and Northampton:Alden Press.45.
2Graeber,A.O.(1999).Forms of knowing mathematics:what preservice teachers should learn.Educational Studies in Mathematics,38.189-208.
3Eisenhart, M., et al.(1993).Complexities of learning to leacher to mathematics for understanding.Journal for Research in Mathematics Education,24(1):8-40.
4Behr, M., Lesh, R, Post, T,, & Silver E. (1983).Rational Number Concepts.ln R.Lesh & M.Landau (Eds.)Acquisition of Mathematics Concepts and Processes.New York:Academic Press.91-125.