1. Antonova, L.A., Ivanov-Kholodnyi, G.S., and Chertoprud, V.E., Aeronomiya sloya E (uchet variatsii UF-izlucheniya i geomagnitnykh vozmushchenii) (Aeronomy of the E Layer (Use of Variations in the UF-Radiation and Geomagnetic Disturbances)), Moscow: Yanus, 1996.
2. Bilitza, D., IRI the international standard for the ionosphere, Adv. Radio Sci., 2018, vol. 16, pp. 1–11.
3. Deminov, M.G. and Shubin, V.N., Empirical model of the location of the main ionospheric trough, Geomagn. Aeron. (Engl. Transl.), 2018, vol. 58, no. 3, pp. 348–355.
4. Gal’perin, Yu.I., Sivtseva, L.D., Filippov, V.M., and Khalipov, V.L., Subavroral’naya verkhnyaya ionosfera (The Subauroral Upper Ionosphere), Novosibirsk: Nauka, 1990.
5. Kouris, S.S. and Muggleton, L.M., Diurnal variation in the E-layer ionization, J. Atmos. Terr. Phys., 1973a, vol. 35, pp. 133–139.