1. Ables, J. G., McCracken, L. G., and Rao, U. R.: 1965,Proc. 9th Int. Cosmic Ray Conf., London 1, 208.
2. Agrawal, S. P.: 1973, Ph. D. Thesis, Physical Research Laboratory, Ahmedabad, India.
3. Agrawal, S. P.: 1981,J. Geophys. Res. 86, 10115.
4. Agrawal, S. P.: 1983,Space Sci. Rev. 34, 127.
5. Agrawal, S. P. and Bercovitch, M.: 1983,Proc. 18th Int. Cosmic Ray Conf., Bangalore 3, 316.