Ladel, S., & Kortenkamp U.  (2009).  Realisations of MERS (Multiple Extern Representations) and MELRS (Multiple Equivalent Linked Representations) in Elementary Mathematics Software.  (Durand-Guerrier, V., Soury-Lavergne S., & Arzarello F., Ed.).Proceedings of the Sixth Congress of the European Society for Research in Mathematics Education. January 28th - February 1st 2009, Lyon (France).  

Kortenkamp, U., & Rolka K.  (2009).  Using Technology in the Teaching and Learning of Box Plots.  (Durand-Guerrier, V., Soury-Lavergne S., & Arzarello F., Ed.).Proceedings of the Sixth Congress of the European Society for Research in Mathematics Education. January 28th - February 1st 2009, Lyon (France).