[Li, Yun-Xiang] Hunan City Univ, Coll Sci, Yiyang 413000, Peoples R China.
[Khan, Sami Ullah] COMSATS Univ Islamabad, Dept Math, Sahiwal 57000, Pakistan.
[Shah, Faqir] Karakoram Int Univ, Dept Math, Gilgit 15100, Pakistan.
[Waqas, Hassan] Govt Coll Univ Faisalabad, Dept Math, 31200 Layyah Campus, Faisalabad, Pakistan.
[Khan, M. Ijaz] Riphah Int Univ I 14, Dept Math & Stat, Islamabad 44000, Pakistan.