1. Department of Basic Science, Faculty of Engineering at Benha, Benha University, Egypt
2. Department of Mathematics, Faculty of Science, Menoufia University, Egypt
3. Department of Mathematics, Zhejiang Normal University, Jinhua, Zhejiang, China
4. Department of Mathematics, King Abdulaziz University, Jeddah, Saudi Arabia
5. Department of Mathematics and Statistics, University of South Florida, Tampa, USA
6. School of Mathematics, South China University of Technology, Guangzhou, China