1. ECARES and Département de Mathématique, Université libre de Bruxelles CP 114/4, Avenue F.D. Roosevelt 50, B-1050 Bruxelles, Belgium
2. Research Center for Statistics, University of Geneva, Bd du Pont d’Arve 40 - CH-1211 Geneva, Switzerland
3. International Institute of Finance, School of Management, University of Science and Technology of China, Hefei, China