1. Department of Mathematics, Bangalore University, Bangalore 560 001, India
2. Department of Mathematics, Gogte Institute of Technology, Belagavi 590 008, India
3. P. G. Department of Mathematics and Research Centre in Applied Mathematics, MES College, Malleswaram, Bangalore 560 003, India
4. Department of Mathematics, Karnatak University, Dharwad 580 003, India