1. Department of Studies in Mathematics, University of Mysore, Manasagangotri, Karnataka, India
2. Universite d’Evry Val d’Essonne, Laboratoire de Mathematiques et Modelisation d’Evry (UMR), I.B.G.B.I. Evry Cedex France
3. Department of Mathematics, School of Physical Sciences, Central University of Karnataka, Karnataka, India