1. Department of Physics, Raghunathpur College, P.O. Raghunathpur 723133 Dist., Purulia (WB), India
2. Department of Physics, Lady Brabourne College, Kolkata-700017, India
3. Institute of Mathematical Sciences, C.I.T. Campus, Taramani, Chennai-600113, India
4. Physics and Applied Mathematics Unit (PAMU), Indian Statistical Institute, Kolkata-700108, India