Institution: | 1. Department of Mathematics, Aristotle University of Thessaloniki, Thessaloniki, 54006 Greece;2. Department of Education, Aristotle University of Thessaloniki, Thessaloniki, 54006 Greece;1. Department of Mathematics, University of Patras, 26500 Patras, Greece;2. Department of Physics, University of Patras, 26500 Patras, Greece |