1. Department of Mathematics, Institute of Statistics; Zhejiang University; Hangzhou 310027 China
2. Department of Statistics, Faculty of Science and Technology; Government College University; Faisalabad Pakistan
3. Department of Statistics, Faculty of Science; University of Sargodha; Sargodha Pakistan
4. Department of Mathematics and Statistics; King Fahad University of Petroleum and Minerals; Dhahran Saudi Arabia