1. Department of Physics, CSR Sarma College, Ongole 523 001, India
2. Department of Applied Physics, Faculty of Engineering and Technology, MS University of Baroda, Vadodara 390 001, India
3. Department of Physics, VRS & YRN College, Chirala 523 157, India
4. Department of Physics, VSR & NVR College, Tenali 522 201, India