1. College of Mathematics and Information Science, Shaanxi Normal University, Xi’an 710062, China
2. Department of Mathematics, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt
3. School of mathematics and statistics, Long Dong University, Qingyang 745000, China
4. School of Mathematics and Computer Science, Northwest University for Nationalities, Lanzhou 730030, China