1. Department of Mathematics, University of Oslo P.O. Box 1053 Blindern, N-0316 Oslo, Norway
2. Norwegian School of Economics and Business Administration (NHH) Helleveien 30, N-5045 Bergen, Norway
3. Department of Probability Theory, Statistics and Actuarial Mathematics Taras Shevchenko National University of Kyiv 64 Volodymyrska, 01601 Kyiv, Ukraine