1. Department of Mathematics, Zhejiang Normal University, Jinhua 321004, Zhejiang, China
2. Department of Mathematics, King Abdulaziz University, Jeddah, Saudi Arabia
3. Department of Mathematics and Statistics, University of South Florida, Tampa, FL 33620, USA
4. College of Mathematics and Physics, Shanghai University of Electric Power, Shanghai 200090, China
5. College of Mathematics and Systems Science, Shandong University of Science and Technology, Qingdao 266590, Shandong, China