1. School of Mathematics and Statistics, Jiangxi Normal University, Nanchang, Jiangxi 330022, People’s Republic of China
2. College of Science and Technology, Jiangxi Normal University, Gongqing City, Jiujiang, Jiangxi 332020, People’s Republic of China
3. Institute of Mathematics, Yunnan University, Kunming, Yunnan 650091, People’s Republic of China