[1] Inst Southern Punjab, Dept Math & Stat, Multan, Pakistan
[2] Univ Lahore, Dept Math, Pakpattan Campus, Pakpattan, Pakistan
[3] Yunnan Normal Univ, Sch Informat Sci & Technol, Kunming, Yunnan, Peoples R China
[4] Anhui Jianzhu Univ, Sch Math & Phys, Hefei 230601, Peoples R China