[Pan, Dong-Dong] Yunnan Univ, Dept Stat, Kunming, Peoples R China.^[Li, Zheng-Bang] Cent China Normal Univ, Sch Math & Stat, Wuhan, Peoples R China.^[Li, Qi-Zhai] Chinese Acad Sci, Acad Math & Syst Sci, Beijing, Peoples R China.^[Fung, Wing Kam] Univ Hong Kong, Dept Stat & Actuarial Sci, Hong Kong, Hong Kong, Peoples R China.