[1] Zhejiang Univ, Dept Math, Hangzhou 310027, Zhejiang, Peoples R China
[2] Guizhou Univ, Coll Math & Stat, Guiyang 550025, Guizhou, Peoples R China
[3] Chang Gung Univ, Grad Inst Business & Management, Coll Management, Taoyuan, Taiwan
[4] Chang Gung Mem Hosp, Dept Nurol, Taoyuan, Taiwan
[5] Zhejiang Gongshang Univ, Dept Math, Hangzhou 310018, Zhejiang, Peoples R China
[6] Guizhou Univ, Coll Math & Stat, Guiyang 550025, Guizhou, Peoples R China