[Zhang, Xinan; Huang, Jicai; Yang, Cuihong; Ruan, Shigui] Cent China Normal Univ, Sch Math & Stat, Wuhan 430079, Hubei, Peoples R China.
[Zou, Lan] Sichuan Univ, Dept Math, Chengdu 610064, Sichuan, Peoples R China.
[Ruan, Shigui; Chen, Jing] Univ Miami, Dept Math, Coral Gables, FL 33146 USA.
[Fang, Yile] Huazhong Univ Sci & Technol, Dept Elect & Elect Educ, Wuchang Branch, Wuhan 430064, Hubei, Peoples R China.
[Zhang, Jinhui] Zhongyuan Univ Technol, Dept Appl Math, Zhengzhou 451191, Henan, Peoples R China.