Affiliation: | 1. Laboratoire de Mathématiques Paul Painlevé, Université de Lille, 59655 Villeneuve d''Ascq Cedex, France;2. Department of Mathematics Education, Korea National University of Education, 28173 Cheongju, South Korea;3. Institut für Algebra, Fachrichtung Mathematik, TU Dresden, 01062 Dresden, Germany;4. Department of Mathematics, Technion, Israel Institute of Technology, Haifa 32000, Israel;1. Fachbereich Mathematik, Universität Hamburg, Bundesstraße 55, 20146 Hamburg, Germany;2. Institut Denis Poisson, CNRS, Université de Tours, Université d''Orléans, Parc de Grandmont, 37200 Tours, France;1. School of Mathematics, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom;2. Department of Mathematics, University of Manchester, Oxford Road M13 6PL, United Kingdom;1. Department of Mathematics, Pedagogical University of Cracow, Podchora??ych 2, PL-30-084 Cracow, Poland;2. Jagiellonian University, Faculty of Mathematics and Computer Science, ?ojasiewicza 6, PL-30-348 Cracow, Poland |