1. Section of Mathematics , Academy of Romanian Scientists , 050094 Bucharest , Romania
2. Department of Computer Science and Engineering , Air University Islamabad , Multan Campus , 60000 , Multan , Pakistan
3. Department of Mathematics , COMSATS University Islamabad , Vehari Campus , 61100 , Vehari , Pakistan
4. Department of Mathematics , Quaid-i-Azam University , Islamabad 44000 , Pakistan