1. Department of Management, Technology and Economics, ETH Zürich, Swiss Federal Institute of Technology, Zürich CH-8092, Switzerland
2. Bogolubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980, Russia
3. Swiss Finance Institute, c/o University of Geneva, 40 Blvd. Du Pont d'Arve, CH 1211 Geneva 4, Switzerland