1. Q. A. Bhatti:
Department of Physics, Shah Abdul Latif University, Khairpur, Pakistan
2. B. A. Malik:
Department of Physics, Shah Abdul Latif University, Khairpur, Pakistan
3. A. H. Bhatti:
Department of Physics, Shah Abdul Latif University, Khairpur, Pakistan
4. F. A. Mangi:
Department of Physics, Shah Abdul Latif University, Khairpur, Pakistan