1. 1) Astafyeva E., S. Shalimov, E. Olshanskaya, and P. Lognonne (2013), Ionospheric response to earthquakes of different magnitudes: Larger quakes perturb the ionosphere stronger and longer, Geophysical Research Letters, vol. 40, 1675–1681, doi:10.1002/grl.50398.
2. 2) Chum J., F. Hruska, J. Zednik, and J. Lastovicka (2012), Ionospheric disturbances (infrasound waves) over the Czech Republic excited by the 2011 Tohoku earthquake, Journal of Geophysical Research, vol. 117, A08319, doi:10.1029/2012JA017767.
3. 3) Hino, M., Spectral analysis, Asakura-shoten, 1977 (in Japanese).
4. 4) International Telecommunication Union (1992), Recommendation ITU-R P.368–7, Ground-wave propagation curves for frequencies between 10 kHz and 30 MHz, P Series, Geneva, Switzerland.
5. 5) International Telecommunication Union (2016), Recommendation ITU-R P.684–7, Prediction of field strength at frequencies below 150 kHz, P Series, Geneva, Switzerland.