1. School of Mathematics and Physics, Lanzhou Jiaotong University, Lanzhou, Gansu 730070, P. R. China
2. Department of Mathematics, College of Science and Humanities in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
3. Department of Mathematics and Engineering Physics, Faculty of Engineering, Mansoura University, Mansoura 35516, Egypt
4. Department of Basic Science, Faculty of Computers and Informatics, Suez Canal University, Ismailia 41522, Egypt
5. School of Law, Zhejiang University of Finance and Economics, Hangzhou, Zhejiang 310018, P. R. China