1. Department Finance of Sustainable, Plekhanov Russian University of Economics, 117997 Moscow, Russia
2. Department of Differential Equations & Mathematic Economics, National Research Saratov State University Chernyshevsky, 410012 Saratov, Russia
3. Department of Tax Policy and Customs Affairs, North-Caucasus Federal University, 355017 Stavropol, Russia
4. Department of Finance, Belgorod National Research University, 308015 Belgorod, Russia