Kafetzopoulos, G. - I., & Psycharis, G. (2016). Conceptualising function as covariation through the use of a digital system integrating CAS and Dynamic Geometry. In C. Csíkos, Rausch, A., & Szitányi, J. (Eds.), Proceedings of the 40th Conference of the International Group for the Psychology of Mathematics Education (PME 40) (Vol. 3, pp. 67-74). Szeged, Hungary: PME.