1. Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
2. Department of Physics, Aliah University, Newtown, Kolkata 700 156, India
3. Acharyya Prafulla Chandra College, New Barrackpore, Kolkata 700 131, India
4. Narula Institute of Technology, Agarpara, Kolkata 700 109, India