A. Fauzan, D. Slettenhaar, und T. Plomp. Proceedings of the 3 rdInternational Mathematics Education and Society Conference. Copenhagen, Denmark: Center for Research in Learning Mathematics, (2002)
H. Forssell. (2011)cite arxiv:1109.0699Comment: 32 pages. This is the first pre-print version, the final revised version can be found at http://onlinelibrary.wiley.com/doi/10.1002/malq.201100080/abstract (posting of which is not allowed by Wiley). Changes in v2: updated comments.