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Ladel, S. , & Kortenkamp, U. . (2013). Number concepts - processes of internalization and externalization by the use of multi-touch technology. In C. Benz, Brandt, B. , Kortenkamp, U. , Krummheuer, G. , Ladel, S. , & Vogel, R. , Early Mathematics Learning. Selected Papers of the POEM 2012 Conference (S. 237-256). New York: Springer Verlag.

Dohrmann, C. , Kortenkamp, U. , & Ladel, S. . (2012). An Activity-Theoretic View on Multitouch Devices in Mathematics Education. In Proceedings. ICME 12. Seoul.

Ladel, S. , & Kortenkamp, U. . (2012). Early maths with multi-touch - an activity-theoretic approach. Working paper. In Proceedings of POEM. Frankfurt.

Ladel, S. , & Kortenkamp, U. . (2011). An activity-theoretic approach to multi-touch tools in early maths learning. Working Paper. In Proceedings of ATATEMLO. Paris.

Ladel, S. , & Kortenkamp, U. . (2011). Finger-symbol-sets and multi-touch for a better understanding of numbers and operations. (M. Pytlak, Rowland, T. , & Swoboda, E. )Proceedings of the Seventh Congress of the European Society for Research in Mathematics Education (CERME 7). Rzeszów, Poland: Congress of the European Society for Research in Mathematics Education (CERME) . Abgerufen von http://cermat.org/sites/default/files/LadelKortenkamp-FMBUNO-2011a.pdf

Ladel, S. , & Kortenkamp, U. . (2011). Implementation of a multi-touch-environment supporting finger-symbol-sets. (M. Pytlak, Rowland, T. , & Swoboda, E. )Proceedings of the Seventh Congress of the European Society for Research in Mathematics Education (CERME 7). Rzeszów, Poland: Congress of the European Society for Research in Mathematics Education (CERME) . Abgerufen von http://www.mathematik.uni-dortmund.de/~erme/doc/cerme7/CERME7.pdf

Ladel, S. . (2011). Multiplex-R: Zum Wechsel zwischen verschiedenen Darstellungsformen von Zahlen und Operationen bei 5- bis 8-jährigen Kindern. (R. Haug & Holzäpfel, L. )Beiträge zum Mathematikunterricht 2011 - Beiträge zur 45. Jahrestagung der Gesellschaft für Didaktik der Mathematik vom 21.02.2011 bis 25.02.2011 in Freiburg. Münster: WTM-Verlag.