LUO Yan 1, 2 , YANG Zhao -jun , ZHANG Wei 3
(1. College of Finance and Statistics, Hunan Univ, Changsha, Hunan 410079, China; 2. School of Mathematics and Statistics, Nanjing Univ of Audit, Nanjing, Jiangsu 210075, China; 3. School of Finance, Nanjing Univ of Audit, Nanjing, Jiangsu 210075, China)