Affiliation: | 1. Department of Mathematics , Quaid-i-Azam University , 45320, Islamabad , 44000 , Pakistan snqau@hotmail.com;3. Department of Mathematics , Quaid-i-Azam University , 45320, Islamabad , 44000 , Pakistan;4. Department of Mathematics , Quaid-i-Azam University , 45320, Islamabad , 44000 , Pakistan;5. Department of Physics , Faculty of Science, King Saud University , P.O. Box 1846 , Riyadh 11321 , Saudi Arabia;6. Department of Physics , Faculty of Science, King Saud University , P.O. Box 1846 , Riyadh 11321 , Saudi Arabia |