Stability problems for stochastic models : proceedings of the Fifteenth Perm Seminar, Perm, Russia, June 2-6, 1992 - Zolotarev, V. M. (Vladimir M.); Kruglov, V. M. (Viktor Makarovich); Korolev, V. I︠U︡. (Viktor I︠U︡révich); International Seminar on Stability Problems for Stochastic Models (Frontiers in pure and applied probability, 1994)