1. B. N. Gershman., Dynamics of Ionospheric Plasma [in Russian], Nauka, Moscow (1974).
2. H. Westin, ?Buoyancy waves in the surface inversion during the subarctic winter,? KGJ Rep., No. 75: 2 (December, 1975).
3. L. M. Brekhovskikh, Waves in Layered Media [in Russian] Nauka, Moscow (1973).
4. L. K. Zarembo and V. A. Krasil'nikov, Introduction to Nonlinear Acoustics [in Russian] Nauka, Moscow (1966)
5. Otkrytiya SSSR-1973, TsNIIPI, Moscow (1974), p. 22.