1. School of Mathematics and Statistics , Nanjing University of Information Science and Technology , Nanjing 210044, Jiangsu ; Center for Applied Mathematics of Jiangsu Province, Nanjing University of Information Science and Technology, Nanjing 210044; and Jiangsu International Joint Laboratory on System Modeling and Data Analysis, Nanjing University of Information Science and Technology, Nanjing 210044 , P. R. China
2. S. M. Nikolskii Mathematical Institute , Peoples’ Friendship University of Russia (RUDN University) , 6 Miklukho-Maklaya Street , Moscow , 117198; and Department of Mechanics and Mathematics, Saratov State University, Astrakhanskaya 83, Saratov 410012 , Russia