1. Department of Statistics, School of Mathematics and Statistics, Jiangsu Normal University, Xuzhou, P.R. China;
2. Department of Mathematics, School of Science, Beijing Technology and Business University, Beijing, P.R. China;
3. Department of Mathematics, Harbin Institute of Technology, Harbin, P.R. China;
4. Department of General Surgery, DongChangFu People’s Hospital, Liaocheng, P.R. China