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2. J. M. Kelso, Radio Ray Propagation in the Ionosphere, McGraw-Hill, London, 1964.
3. K. G. Budden, Radio Waves in the Ionosphere, The University Press, Cambridge, 1961.
4. V. L. Ginzburg, The Propagation of Electromagnetic Waves in a Plasma [in Russian], Fizmatgiz, Moscow, 1960.
5. O. E. H. Rydbeck, On the Propagation of Radio Waves, Göteborg, 1944.