Ladel, S., & Kortenkamp U.  (Submitted).  Number concepts ?- processes of internalization and externalization by the use of multi-touch technology Silke Ladel and Ulrich Kortenkamp.  Early Mathematics Learning.  

[Gast]  (2014).  Early Mathematics Learning.  (Kortenkamp, U., Brandt B., Benz C., Krummheuer G., Ladel S., & Vogel R., Ed.). 

Ladel, S., & Kortenkamp U.  (2013).  An activity-theoretic approach to multi-touch tools in early maths learning.  The International Journal for Technology in Mathematics Education. 20, 

Ladel, S., & Kortenkamp U.  (2013).  Designing a technology based learning environment for place value using artifact-centric activity theory.  (Lindmeier, A. M., & Heinze A., Ed.).Proceedings of the 37th conference of the International Group for the Psychology of Mathematics Education. Mathematics learning across the life span. 1, 188-192.

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

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

Ladel, S., & Kortenkamp U.  (2011).  Finger-Symbol-Sets and Multi-Touch for a better understanding of numbers and operations.  Proceedings of CERME 7, Rzeszow.  

Ladel, S., & Kortenkamp U.  (2011).  Implementation of a multi-touch-environment supporting finger symbol sets.  Proceedings of CERME 7, Rzeszow.  

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).  

Ladel, S., & Kortenkamp U.  (2009).  Virtuell-enaktives Arbeiten mit der ?Kraft der Fünf''.  MNUprimar.