1. School of Mathematics and Statistics, Southwest University, Chongqing, People's Republic of China
2. Department of Mathematical Sciences, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
3. School of Information and Mathematics, Yangtze University, Jingzhou, People's Republic of China
4. College of Management, Chongqing College of Humanities, Science & Technology, Chongqing, People's Republic of China
5. School of Mathematics and Information Science, North Minzu University, Yinchuan, People's Republic of China