1. Department of Informatics and Mathematics, Moravian Business College Olomouc, tř. Kosmonautů 1288/1, 77900 Olomouc, Czech Republic
2. Department of Sciences and Methods for Engineering, University of Modena and Reggio Emilia, Via G. Amendola, 2-Pad. Morselli, 42122 Reggio Emilia, Italy