1. Department of Physics, Barasat Government College, Kolkata 700 124, North 24 Parganas, West Bengal, India
2. Department of Mathematics, Jadavpur University, Kolkata 700 032, West Bengal, India
3. Satyabharati Vidyapith, Barasat, North 24 Parganas, Kolkata 700 126, West Bengal, India