1. National Center for Mathematics Education, University of Gothenburg Vera Sandbergs Allé 5A, Gothenburg Sweden
2. Instituto Politécnico Nacional, CICATA Legaria, Programa de Matemática Educativa Calzada Legaria No. 694, Col. Irrigación, C.P. 11500, Alcaldía Miguel Hidalgo, Mexico City Mexico
3. Department of Science Education, University of Copenhagen Universitetsparken 1, Copenhagen Denmark
4. Department of Science, Weizmann Institute of Science Rehovot Israel
5. Danish School of Education, Aarhus University Tuborgvej 164, Copenhagen Denmark