1. Department of Mathematics, St. Xavier's College (Autonomous), Palayamkottai 627 002, Tamil Nadu, India
2. Affiliated to Manonmaniam Sundaranar University, Abishekapatti, Tirunelveli 627 012, Tamil Nadu, India
3. PG and Research Department of Mathematics, St. Xavier's College (Autonomous), Palayamkottai 627 002, Tamil Nadu, India