1. Department of Statistics, Quaid-i-azam University, Islamabad, Pakistan
2. Department of Mathematics and Statistics, The University of Haripur, Haripur, Pakistan
3. Department of Mathematics, College of Science and Humanities in Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj, Saudi Arabia
4. Department of Mathematics, Faculty of Science, Mansoura University, Mansoura, Egypt