[Song, Ying-Qing] Hunan City Univ, Sch Sci, Yiyang 413000, Peoples R China.
[Javid, Khurram] Northern Univ, Dept Math, Wattar Wallai Rd, Nowshera 24110, Pakistan.
[Khan, Sami Ullah] COMSATS Univ Islamabad, Dept Math, Sahiwal 57000, Pakistan.
[Khan, M. Ijaz] Riphah Int Univ, Dept Math & Stat, I-14, Islamabad 44000, Pakistan.
[Sun, Tian-Chuan] Huzhou Univ, Qiuzhen Coll, Huzhou 313000, Peoples R China.