Muller, G. “Earth-Flattening Approximation for Body Waves Derived from Geometric Ray Theory - Improvements, Corrections and Range of Applicability”. Journal of Geophysics 42, no. 1 (April 8, 1976): 429-436. Accessed September 18, 2025. https://journal.geophysicsjournal.com/JofG/article/view/89.