1. Department of Mathematics, Quaid-I-Azam University, Islamabad 44000, Pakistan
2. Department of Mathematics, College of Sciences, King Khalid University, Abha 61413, Saudi Arabia
3. Department of Mathematics, Çankaya University, 06790 Etimesgut, Ankara, Turkey
4. Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan