[1] Quaid I Azam Univ, Dept Math, Islamabad, Pakistan
[2] King Abdulaziz Univ, Nonlinear Anal & Appl Math NAAM Res Grp, Fac Sci, Jeddah, Saudi Arabia
[3] Riphah Int Univ, Dept Math, Islamabad, Pakistan
[4] Univ Sci & Technol China, Sch Math Sci, Hefei 230026, Anhui, Peoples R China