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2. Budden K. G., Clemmow P. C., Proc. Camb. Phil. Soc.53 (1957), 669.
3. Budden K. G., Radio Waves in the Ionosphere. Cambridge University Press, London 1961; chapters 18 and 19.
4. Budden K. G., Lectures on Magnetoionic Theory. Blackie, London and Glasgow 1964; chapter 4.
5. Heading J., J. Res. NBS (Radio Prop.)65D (1961), 595.