Institution: | Departmentof Mathematics, University of Gunma, Hoshikuki-cho 798-8, Chuou-Ward, Chiba, 260-0808, Japan,Faculty of Mathematics and Natural Sciences, University of Rzeszow, Prof. Pigonia''s Street 1, 35-310 Rzeszow, Poland and School of Mathematics and Statistics, Chifeng University, Chifeng 024000, Inner Mongolia, China |