Affiliation: | (1) Department of Mathematics, Quaid-i-Azam University, 45320, 44000 Islamabad, Pakistan;(2) Present address: Department of Condensed Matter Physics, Main Building, Strada Costeira 11, 34014 ICTP, Trieste, Italy;(3) College of Aeronautical Engineering, National University of Sciences and Technology, PAF Academy, 24090 Risalpur, Pakistan |