1. Insitute of Mathematics named after V.I. Romanovsky of the Academy of Sciences of the Republic of Uzbekistan, Universitetstkaya str. 9, 100174, Tashkent, Uzbekistan
2. Namangan State University, Uyci str. 316, 160136, Namangan, Uzbekistan
3. Andijan State University, Universitetstkaya str. 129, 170100, Andijan, Uzbekistan