1. Faculty of Mathematics, University of Duisburg-Essen, D-45127 Essen, Germany
2. Weierstrass Institute Berlin, Stochastic Algorithms and Nonparametric Statistics, D-10117 Berlin, Germany
3. Department of Quantitative Economics, University of Amsterdam, 1001 NJ Amsterdam, Netherlands
4. Institute of Insurance Science and Institute of Financial Mathematics, Faculty of Mathematics and Economics, Ulm University, D-89069 Ulm, Germany