Author/Authors :
Braathe، نويسنده , , Hans-Jّrgen، نويسنده ,
Abstract :
This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).
rticle has been retracted at the request of the Author and the Authorʹs institution.
ticle was a duplication of a paper that had already appeared in Gunnarsdottir, G.H., Hreinsdottir, F., Palsdottir, G., Hannula, M., Hannula-Sormunen, M., Jablonka, E., Jarnkvist, U.T., Ryve, A., Valero, P., & Wæge, K.(Eds. 2012) Proceedings of NORMA 11. The sixt Nordic Conference on Mathematics Education in Reykjavik, May 11–14, 2011. Pp. 197–206. University of Iceland Press, Reykjavik, Iceland. ISBN 978-9997-54-965-9. The author would like to apologize for this error on his part.