1. Behr, M., Hare, G., Post, T., & Lesh, R. (1992). Rational number, ratio and proportion. D. A.
2. Grouws. (Ed.), Handbook of Research on Mathematics Teaching and Learning (pp. 17-43). New York: Simon & Schuster Macmillan.
3. Cramer, K., & Post, T. (1993). Connecting research to teaching: Proportional reasoning. The Mathematics Teacher, 86, 404–407. doi:10.5951/MT.86.5.0404
4. Cramer, K., Post, T., & Currier, S. (1993). Learning and teaching ratio and proportion: Research implications. D. T. Owens (Ed.), Research ideas for the classroom: Middle grades mathematics (pp. 159–178). New York: Macmillan.
5. De Bock, D., Van Dooren, W., Janssens, D., & Verschaffel, L. (2002). Improper use of linear reasoning: An in-depth study of the nature and the irresistibility of secondary school students’ errors. Educational Studies in Mathematics, 50, 311–314. doi:10.1023/A:1021205413749