Psycharis, G., & Kynigos, C. (2004). Normalising geometrical constructions: A context for the generation of meanings for ratio and proportion. In M. J. Høines & Fuglestad, A. B. (Eds.), Proceedings of the 28th Conference of the International Group for the Psychology of Mathematics Education (PME 28) (Vol. 4, pp. 65-72). Bergen, Norway.