1. School of Mathematics, Nanjing University of Aeronautics and Astronautics, Nanjing 211100, China
2. School of Mathematics and Statistics, Linyi University, Linyi, Shandong 276005, China
3. Department of Mathematics, Islamia College Peshawar, Peshawar 25120, Pakistan
4. Department of Mathematics, College of Science, King Khalid University, Abha 61413, Saudi Arabia