@inproceedings{3d177703cea946e8a24196f68555eb93,
title = "Designing instruction on proportional reasoning with average speed",
author = "K.P.E. Gravemeijer and \{Galen, van\}, F.H.J. and R. Keijzer",
year = "2005",
language = "English",
volume = "1",
pages = "103--108",
editor = "Chick, \{Helen L.\} and Vincent, \{Jill L.\}",
booktitle = "Proceedings of the 29th Conference of the International Group for the Psychology of Mathematics Education (PME 29), 10-15 july 2005, Melbourne, Australia",
publisher = "Dept. of Science and Mathematics Education, University of Melboune",
}