1. Econophysica Ltd., Annecy Court, Ferry Works, Summer Road, Thames Ditton, Surrey KT7 0QJ, UK
2. Department of Mathematics, Faculty of Engineering, Czech University of Life Sciences Prague, Kamýcká 129, Prague 16500, Czech Republic
3. Department of Mathematics, Faculty of Informatics and Statistics, Prague University of Economics and Business, Ekonomická 957, Prague 14800, Czech Republic