1. S Chatterjee, Indian J. Phys. B74, 363 (2000)
2. S Chatterjee and V C Vani, Bull. Astron. Soc. India 30, 835 (2002)
3. S Chatterjee and V C Vani, J. Mod. Opt. 50, 833 (2003)
4. V C Vani and S Chatterjee, Bull. Astron. Soc. India 31, 457 (2003)
5. V C Vani and S Chatterjee, Curr. Sci. 86, 177 (2004)