Shushkevich, Gennady. “Propagation of the Sound Wave by an Unclosed Spherical Shell and a Penetrable Ellipsoid”. Advances in Mechanical and Materials Engineering 33, no. 293 (3) (October 28, 2016): 221-232. Accessed July 3, 2024. https://journals.prz.edu.pl/amme/article/view/1321.