1. Albin Sancta J, Gnana Sutha A, Freeda T H, Mahadevan C and Balasingh C 2001Indian J. Phys. A75 245
2. George A W 1989Nucl. Instrum. Meth. Phys. Res. B39 708
3. Harris L B and Vella G J 1966J. Appl. Chem. 17 151
4. Jain S C and Dahake S L1964Indian J. Pure and Appl. Phys. 2 71
5. Keeffe M O and Perrino C T 1967J. Phys. & Chem. Solids 28 211