1. Department
of Physics, University of the Free State, P. O. Box 339, Bloemfontein ZA9300, South Africa
2. Department
of Chemistry, Dr. B. R. Ambedkar National Institute of Technology, Jalandhar, Punjab 144011, India
3. Department
of Chemistry, Bahra University, Waknaghat (Shimla Hills) 173234, District Solan, Himachal Pradesh, India