1. Department of Mathematics, Aligarh Muslim University, Aligarh 202 002, India
2. Department of Mathematics, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt
3. Department of Mathematics, Faculty of Science, King Khalid University, Abha 9004, Saudi Arabia
4. Department of Mathematics, Bengal Engineering and Science University, Shibpur, Howrah, West Bengal 711103, India