1. 1 Department of Mathematics , University of Mazandaran , Babolsar , Iran
2. 2 Department of Mathematical Sciences , University of South Africa , South Africa
3. 3 School of Liberal Studies , Dr B R Ambedkar University Delhi , Delhi , India
4. 4 Department of Mathematics, Amity School of Applied Science , Amity University Rajasthan , Jaipur , India
5. 5 Department of Mathematics , SGND Khalsa College, University of Delhi , Delhi , India
6. 6 Department of Mathematics, Rajdhani College , University of Delhi , Delhi , India