1. Shanghai University of Finance and Economics Zhejiang College, Jinhua, Zhejiang, China
2. Department of Statistics, Yazd University, P. O. Box 89175-741, Yazd, Iran
3. Department of Statistics, Bahauddin Zakariya University, Multan, Pakistan
4. Department of Mathematics, Faculty of Science, Helwan University, Cairo, Egypt
5. Statistics Department, Faculty of Science, University of Tabuk, Tabuk, Saudi Arabia
6. Department of Statistics and Operations Research College of Science, King Saud University, P.O.Box 2455, Riyadh 11451, Saudi Arabia