1. Department of Statistics, Quaid-i-Azam University, Islamabad, Pakistan
2. Department of Community Medicine, Wah Medical College, National University of Medical Sciences, Rawalpindi, Pakistan; ;
3. Department of Mathematics, College of Sciences and Arts (Muhyil), King Khalid University, Muhyil, Saudi Arabia
4. Mathematics Department, College of Humanities and Science, Prince Sattam Bin Abdulaziz University, Al Aflaj, Saudia Arabia
5. Mathematics Department, Prince Sattam Bin Abdulaziz University, Al-Kharj, Saudi Arabia