1. Department of Mathematics and Descriptive Geometry, Faculty of Civil Engineering, Brno University of Technology, 60200 Brno, Czech Republic
2. Department of Mathematics, Faculty of Electrical Engineering and Communication, Brno University of Technology, 61600 Brno, Czech Republic
3. Department of Cybernetics, Taras Shevchenko National University of Kyiv, Kyiv 01601, Ukraine