1. Department of Mathematics , PSG College of Arts & Science , Coimbatore - 641 014 , Tamil Nadu, India
2. Department of Mathematics, Faculty of Art and Sciences , Cankaya University , 06530 Ankara , Turkey and Institute of Space Sciences , Magurele- Bucharest , Romania .
3. Department of Mathematics , C. B. M. College , Kovaipudur, Coimbatore - 641 042 , Tamil Nadu, India .