1. Department of Stochastic; MTA-BME stochastic Research Group; Budapest University of Technology and Economics; P.O. Box 91 1521 Budapest Hungary
2. Einstein Institute of Mathematics; Hebrew Univeristy of Jerusalem; Edmund J. Safra Campus, Givat Ram Jerusalem 9190401 Israel
3. Institute of Mathematics; Polish Academy of Sciences; ul. Śniadeckich 8 00-656 Warszawa Poland