1. Institut für Mathematik, Universität Potsdam, Potsdam, Germany
2. Modal’X, Université Paris-Nanterre, Nanterre and CREST, Paris, France
3. CEREMADE, Université Paris-Dauphine and CREST, Paris, France
4. CREST, ENSAE and Institut Polytechnique de Paris, Paris, France
5. Tsinghua University, Beijing, China and Shanghai Qi Zhi Institute, Shanghai, China