1. Department of Mathematics, Abdul Wali Khan University Mardan, Pakistan
2. Mathematics Department, Faculty of Sciences, Umm Al-Qura University, Makkah, Saudi Arabia
3. Department of Mathematics, College of Science, Qassim University, Buraydah, Saudi Arabia
4. School of Mathematical Sciences, Jiangsu University, Zhenjiang, P.R. China
5. Department of Mathematics, College of Science, King Khalid University, Abha, Saudi Arabia