LEVSHIN, A. L., and G. F. PANZA. “Further Remarks on Extra Roots of Rayleigh Equation and Somigliana Waves”. Annals of Geophysics 23, no. 1 (November 25, 1970): 45–55. Accessed March 28, 2024. https://www.annalsofgeophysics.eu/index.php/annals/article/view/5142.