Rozhnoi, Alexander, Maria Solovieva, Pier Francesco Biagi, Konrad Schwingenschuh, and Masashi Hayakawa. “Low Frequency Signal Spectrum Analysis for Strong Earthquakes”. Annals of Geophysics 55, no. 1 (April 24, 2012). Accessed October 19, 2021. https://www.annalsofgeophysics.eu/index.php/annals/article/view/5076.