BETRO, B., M. DI NATALE, M. STUCCHI, and G. ZONNO. “Some Considerations on the Hypocentre Location Problem”. Annals of Geophysics 34, no. 1 (November 25, 1981): 161–187. Accessed October 16, 2021. https://www.annalsofgeophysics.eu/index.php/annals/article/view/4694.