Bezuk, N., & Bieck, M. (1993). Current research on rational numbers and common fractions: Summary and implications for teachers. In D. Owens (Ed.), Research ideas for the classroom: Middle grade mathematics. NY: MacMillan.
 Borko, H., Eisenhart, M., Brown, C., Underhill, R., Jones, D., & Agard, P. (1992). Learning to teach hard mathematics: Do novice teachers and their instructors give up too easily? Journal for Research in Maths Edu-cation, 23, 194-222. http://dx.doi.org/10.2307/749118
 Mack, N. (1990). Learning fractions with understanding: Building on informal knowledge. Journal for Research in Mathematics Education, 21, 16-32. http://dx.doi.org/10.2307/749454
 Moss, J., & Case, T. (1999). Developing children’s understanding of the rational numbers: A new model and an experimental curriculum. Journal for Research in Mathematics Education, 30, 122-148. http://dx.doi.org/10.2307/749607
 Newstead, K., & Murray, H. (1998). Young students’ constructions of fractions. In A. Olivier, & K. Newstead (Eds.), Proceedings of the 22nd Conference of the International Group for the Psychology of Mathematics Education, 3, 295-303. Stellenbosch, South Africa.
 Pitkethly, A., & Hunting, R. (1996). A review of recent research in the area of initial fraction concepts. Educational Studies in Mathematics, 30, 5-38. http://dx.doi.org/10.1007/BF00163751
 Saxe, G. B., Taylor, E..V., McIntosh, C., & Geahart, M. (2005). Representing fractions with standard notations: A development analysis. Journal for Research in Ma-thematics Education, 36, 137-157.
 Stafylidous, S., & Vosniodou, S. (2004). The development of students’ understanding of the numerical value of fractions. Learning and Instruction, 14, 503-518. http://dx.doi.org/10.1016/j.learninstruc.2004.06.015
 Tzur, R. (1999). An integrated study of children’s construction of improper fractions and the teachers role in promoting that learning, Journal for Research in Mathematics Education, 30, 390-416. http://dx.doi.org/10.2307/749707