1. Technische Universität Dresden, Faculty of Mathematics, Institute of Mathematical Stochastics, Zellescher Weg 25, 01069 Dresden, Germany
2. Department of Mathematics, University of Zagreb, Bijenička cesta 30, 10000 Zagreb, Croatia
3. Department of Applied Mathematics, Faculty of Electrical Engineering and Computing, University of Zagreb, Unska 3, 10000 Zagreb, Croatia