1. Castelli, J., and Aarons, J., Solar System Radio Astronomy (edit. by Aarons, J.), 49 (Plenum Press, 1965).
2. Bonvini, L. A., Croom, D. L., and Gordon-Smith, A. C., J. Atmos. Terr. Phys., 28, 891 (1966).
3. Allen, C. W., Radio Astronomy, I. A. U. Symp. No. 4 (edit. by Van De Hulst, H. C.), 253 (Cambridge University Press, 1957).
4. Castelli, J. P., and Straka, R. M., Sky and Telescope, 32, 84 (1966).
5. Piatelli, M., and Tofani, G., Osservazioni e Mem. dell'Osserv. Astrofis. di Arcetri, 85, 55 (1967).