Affiliation: | 1. School of Mathematical Sciences, Hebei International Joint Research Center for Mathematics and Interdisciplinary Science, Hebei Normal University, Shijiazhuang 050024, PR China;2. Technion – Israel Institute of Technology, CS Taub Building, Haifa 3200003, Israel;3. Chelyabinsk State University, 129 Bratiev Kashirinykh st., Chelyabinsk 454021, Russia |