1. School of Information and Mathematics, Yangtze University, Jingzhou 434023, People’s Republic of China
2. Department of Mathematics and Information Science, Wenzhou University, Wenzhou 325035, China
3. School of Sciences, Nantong University, Nantong 226019, People’s Republic of China
4. Department of Mathematics and Statistics, Auburn University, 221 Parker Hall, Auburn, Alabama 36849, USA