[Song, Ying-Qing] Hunan City Univ, Coll Sci, Yiyang 413000, Peoples R China.
[Waqas, Hassan; Farooq, Umar] Govt Coll Univ Faisalabad, Dept Math, Layyah Campus, Faisalabad 31200, Pakistan.
[Al-Khaled, Kamel] Jordan Univ Sci & Technol, Dept Math & Stat, POB 3030, Irbid 22110, Jordan.
[Khan, Sami Ullah] COMSATS Univ Islamabad, Dept Math, Sahiwal 57000, Pakistan.
[Khan, M. Ijaz] Riphah Int Univ, Dept Math, I-14, Islamabad 44000, Pakistan.