Änderungen

*2007 Invited Guest Professor at Centro de Estudios de Postgrado y de Investigación en Educación Superior, Universidad Mayor de San Andrés, La Paz (Bolivia)

*2007 Invited Guest Professor at Centro de Estudios de Postgrado y de Investigación en Educación Superior, Universidad Mayor de San Andrés, La Paz (Bolivia)

*2004 - 2010 University Professor for Mathematics Education, Department of Educational Science, [[Universität Hamburg]]

*2004 - 2010 University Professor for Mathematics Education, Department of Educational Science, [[Universität Hamburg]]

*2004 Invited Guest Professor at Department of Mathematics, Johann Wolfgang [[Goethe-Universität Frankfurt]]

*2004 Invited Guest Professor at Department of Mathematics, Johann Wolfgang [[Universität Frankfurt|Goethe-Universität Frankfurt]]

*2002 Habilitation at Department of Educational Science and Psychology, [[Freie Universität Berlin]]

*2002 Habilitation at Department of Educational Science and Psychology, [[Freie Universität Berlin]]

*2001 - 2002Guest Professor at Department of Educational Science, Universidad Metropolitana de Ciencias de la Educación, Santiago de Chile

*2001 - 2002Guest Professor at Department of Educational Science, Universidad Metropolitana de Ciencias de la Educación, Santiago de Chile