1. School of Mathematics and Statistics, Northeast Petroleum University, Daqing Heilongjiang 163318, P. R. China
2. School of Management and Data-Mining Research Center, Xiamen University, Xiamen Fujian 361005, P. R. China
3. Department of Statistics, Xiamen University, Xiamen, Fujian 361005, P. R. China
4. Department of Statistics, Tamkang University, New Taipei City 25137, Taiwan