1. N. Carrara, M. T. De Giorgio, and P. F. Pellegrini, Space Sci. Rev.,11, 555 (1970).
2. P. E. Krasnushkin, The Method of Normal Waves as Applied to Long-Distance Radio Communication [in Russian], Moscow State Univ. (1947), p. 24.
3. V. A. Fok, L. A. Vainshtein, and M. G. Belkina, Radiotekh. Élektron.,1, No. 5, 575 (1956).
4. H. T. Chang, Radio Sci.,6, No. 4, 465 (1971).
5. N. D. Borisov and A. V. Gurevich, in: A Study of the Superlong-Distance Propagation of Short Radio Waves [in Russian], IZMIRAN, Moscow (1975), p. 3.