1. Faculty of Science and Faculty of Natural Sciences, Mathematics and Kinesiology, University of Split, Teslina 12, 21000 Split, Croatia
2. Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška cesta 160, SI-2000 Maribor, Slovenia
3. Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana, Slovenia
4. Institute of Mathematics, Physics and Mechanics, Jadranska 19, SI-1000 Ljubljana, Slovenia