1. Agrawal, P. C., Damle, S. V., Gokhale, G. S., George Joseph and Menon, M. G. K.Proc. Int. Conf. cosmic Rays, London, 1965,1, 453.
2. Aizu, H., Ito, K. and Koshiba, M.Suppl. Prog. Theo. Phys., 1964,30, 134.
3. Aller, L. H...The Abundance of the Elements, Interscience Publishers, New York, 1961.
4. Apparao, M. V. K...Phys. Rev., 1961,123, 295;J. Geophys. Res., 1962,67, 1289.
5. Badhwar, G. D. and Daniel, R. R.Prog. Theo. Phys. Japan, 1963,30, 615.