1. Armstrong, J. W., Coles, W. A., and Harmon, J. K.: 1973, Department of Applied Physics and Information Science preprint, University of California, San Diego, U.S.A.
2. Barnes, A.: 1971,J. Geophys. Res. 76, 7522.
3. Bavassano, B., Mariani, F., and Ness, N. F.: 1973,J. Geophys. Res. 78, 4535.
4. Bezrukikh, V. V., Gringauz, K. I., Zastenker, G. N., and Khokhlov, K. Z.: 1973, preprint, IAGA Scientific Symposium, 15 September, Kyoto, Japan.
5. Burlaga, L. F.: 1972, in E. R. Dyer (General ed.),Solar Terrestrial Physics 1970: Part II, p. 135, D. Reidel Publishing Co., Dordrecht-Holland.