1. Anderson, E. S., Ann. Rev. Microbiol., 22, 131 (1968).
2. Smith, H. W., Nature, 218, 728 (1968).
3. Chabbert, Y. A., Baudens, J. G., and Bouanchaud, D. M., in Bacterial Episomes and Plasmids (edit. by Wolstenholme, G. E. W., and O'Connor, M.), 227 (Churchill, London, 1969).
4. Vimala, K. N., thesis, University of Calicut (1972).
5. Vimala, K. N., and Paniker, C. K. J., Ind. J. Med. Res., 60 (in the press).