1. Department of Physics, University of the Free State, P. O. Box 339, Bloemfontein 9300, South Africa. & Junior High School Balbhadrapur, Ramnagar, Jaunpur-222137, Uttar Pradesh, India.
2. Department of Chemistry, Bharat Sevak Samaj College, Supaul, B. N. Mandal University, Bihar, India.
3. Department of Physics, University of the Free State, P. O. Box 339, Bloemfontein 9300, South Africa. & Department of Physics, The University of the West Indies, St. Augustine, Trinidad and Tobago.
4. Department of Physics, University of the Free State, P. O. Box 339, Bloemfontein 9300, South Africa.