1. Department of Mathematical Modeling, Samarkand State University, University Blv. 15, Samarkand 140104, Uzbekistan
2. V.I. Romanovski Institute of Mathematics, Academy of Sciences, Tashkent 100174, Uzbekistan
3. Department of General and Exact Subjects, Tashkent State University of Economics, Tashkent 100066, Uzbekistan
4. Department of Law and Economics, University “Mediterranea” of Reggio Calabria, 89124 Reggio Calabria, Italy