1. Department of Economics, Society and Politics, University of Urbino, Carlo Bo, Italy ().
2. Department of Finance, VŠB - Technical University of Ostrava, Ostrava, Czech Republic, and DiMSEFA, Catholic University of the Sacred Heart, Milan, Italy ().
3. Department of Economics, University of Bamberg, Bamberg, Germany (, ).
4. Institute of Mathematics, NAS of Ukraine, and Kyiv School of Economics, Kyiv, Ukraine ().