1. Department of Economics and Finance, University of Tyumen, 6 Volodarskogo St., 625003 Tyumen, Russia
2. Department of Fundamental Mathematics and Mechanics, University of Tyumen, 6 Volodarskogo St., 625003 Tyumen, Russia
3. Department of Risk Management and Insurance, St. Petersburg University, 7/9, Universitetskaya Emb., 199034 St. Petersburg, Russia