Änderungen

* [[EMS]]  European Mathematical Society) Member of  the Committee of Education of ESM (1988-1992);     

* [[EMS]]  European Mathematical Society) Member of  the Committee of Education of ESM (1988-1992);     

* [[GDM]]  German Society for Mathematics Education) Scientific Advisory Board (1988-1994);     

* [[GDM]]  German Society for Mathematics Education) Scientific Advisory Board (1988-1994);     

{{gdmbeirat|1986|1991}}

{{gdmbeirat|1986|1992}}

* [[GTZ]]  German Society for Technological Collaboration:  Expert-Consultant and Evaluator of an Indonesian Mathematics and Science Project 1990     

* [[GTZ]]  German Society for Technological Collaboration:  Expert-Consultant and Evaluator of an Indonesian Mathematics and Science Project 1990     

* [[ICMI]]  International Commission of Mathematics Instruction) regular Topic-Group and Discussion-Group organizer on congresses of ICMI, Member of IPC of ICME 11 in Mexico 2008     

* [[ICMI]]  International Commission of Mathematics Instruction) regular Topic-Group and Discussion-Group organizer on congresses of ICMI, Member of IPC of ICME 11 in Mexico 2008