1. Walsh, D., Haddock, F. T., and Schulte, H. F., Space Res., 4 (edit. by Muller, P.), 935 (1964).
2. Hugenin, G. R., Lilley, A. E., McDonough, W. H., and Papagiannis, M. D., Planet. Space Sci., 12, 1137 (1964).
3. Stone, R. G., Alexander, J. K., and Weber, R. R., Planet. Space Sci., 14, 1007 (1966).
4. Harvey, C. C., Ann. d'Astrophys., 28, 248 (1965).
5. Hartz, T. R., Satellite Observations of Ionospheric Radio Noise, Progress in Radio Science 1963–1966, 1109 (URSI, 1967).