1. Section of Mathematics , Academy of Romanian Scientists , 050094 Bucharest , Romania
2. Department of Theoretical Mechanics , Technical University of Iasi , Iasi 700050 , Romania
3. Department of Computer Science and Mathematics , Air University Multan , Multan Campus (60000) , Multan , Pakistan
4. Department of Mathematics , COMSATS University Islamabad , Vehari Campus (61100) , Islamabad , Pakistan