1. Center of Mathematics for Applications, University of Oslo, PO BOX 1053 Blindern, N-0316 Oslo, Norway
2. Norwegian School of Economics and Business Administration, Helleveien 30, N-5045 Bergen, Norway
3. Mathematical Finance, Technische Universität München, Parkring 11, D-85748 Garching-Hochbruck, Germany
4. Department of Mathematics, University of Cologne, Weyertal 86–90, 50931 Cologne, Germany