1. School of Business, University of Leicester, Brookfield, Leicester LE2 1RQ, UK
2. Department of Statistics and Econometrics, Bucharest University of Economic Studies, 6 Piata Romana, 1st District, 010374 Bucharest, Romania
3. Physics, GRAPES (Group of Researchers for Applications of Physics in Economy and Sociology), 483 Rue de la Belle Jardiniere, B-4031 Liege, Belgium