1. Branch of Mazandaran, Statistical Center of Iran, Tehran, Iran
2. Department of Statistics, College of Basic Sciences, Yadegar-e-Imam Khomeini(RAH) Shahr-e-Rey Branch, Islamic Azad University, Tehran, Iran
3. Department of Statistics, Shahid Beheshti University, Tehran, Iran
4. Islamic Azad University, Qaemshahr Branch, Department of Mathematics, Qaemshahr, Iran
5. School of Mathematics, University of Manchester, United Kingdom