1. Bakar, M., & Tall, D. (1992). Students’ mental prototypes for functions and graphs. International Journal of Mathematics Education in Science & Technology, 23(1), 39–50.
2. Ball, D. L., & Bass, H. (2003). Toward a practice-based theory of mathematical knowledge for teaching. Paper presented at the 2002 Annual Meeting of the Canadian Mathematics Education Study Group. Edmonton, AB: CMESG/GCEDM.
3. Ball, D. L., Hill, H. C., & Bass, H. (2005). Knowing mathematics for teaching: Who knows mathematics well enough to teach third grade, and how can we decide? American Educator, 29, 14–22.
4. Barton, B. (2009). The Klein project: A living and connected view of mathematics for teachers. An IMU/ICMI collaboration: A short description. MSOR Connections, 8(4), 16–17. http://mathstore.gla.ac.uk/headocs/84Barton_B.pdf . Accessed 3 Sep 2012.
5. Bauer, L. (2011). Mathematik, Intuition, Formalisierung. eine Untersuchung von Schülerinnen und Schülervorstellungen zu. $$ 0,\overline{9} = 1 $$ Journal für Mathematik-Didaktik, 32(1), 79–102.