1. Appel, K., & Haken, W. (1977). Every planar map is four colorable. Part I: Discharging. Illinois Journal of Mathematics, 21(3), 429–490.
2. Ball, D. (2000). Working on the inside: Using one’s own practice as a site for studying teaching and learning. In A. E. Kelly & R. A. Lesh (Eds.), Handbook of research design in mathematics and science education (pp. 365–402). Mahwah, NJ: Lawrence Erlbaum Associates. https://eric.ed.gov/id=ED478318.
3. Baron, L. M. (2010). Helping teachers generate better homework: MAA makes time for WeBWorK. MAA Focus, 30(5), 18–19.
4. Battista, M. (2001). Shape makers. Computers in the Schools, 17(1–2), 105–120. https://doi.org/10.1300/jo25v17n01_09 .
5. Battista, M. (2003). Shapemakers. Emeryville, CA: Key Curriculum Press.