1. Mäntän lukio, P.O. Box 87, FI-35801 Mänttä, Finland
2. Department of Mathematics, Statistics and Philosophy, FI-33014 University of Tampere, Finland
3. Oulun Lyseon Lukio, Kajaaninkatu 3, FI-90100 Oulu, Finland
4. Savonlinna Department of Teacher Education, University of Joensuu P.O.Box 86, FI-57101 Savonlinna, Finland