Affiliation: | 1. School of Mathematics and Statistics, Henan University of Science and Technology, Luoyang 471003, China;2. Faculty of Mathematics and Statistics, Hubei Key Laboratory of applied mathematics, Hubei University, Wuhan 430062, China;3. Department of Informatics, University of Bergen, Bergen N-5020, Norway;4. College of Mathematics and Systems Science, Shandong University of Science and Technology, Qingdao, 266590, China |