[1] Wuhan Univ, Sch Math & Stat, Wuhan 430072, Peoples R China
[2] Wuhan Text Univ, Sch Math & Phys Sci, Wuhan 430200, Peoples R China
[3] Cent China Normal Univ, Sch Math & Stat, Wuhan 430079, Peoples R China
[4] Cent China Normal Univ, Hubei Key Lab Math Sci, Wuhan 430079, Peoples R China
[5] Univ Missouri, Dept Stat, Columbia, MO USA
[6] Zhongnan Univ Econ & Law, Sch Stat & Math, Wuhan 430073, Peoples R China