Nicomedes, W. L., Bathe, K.-J., Moreira, F. J. S. and Mesquita, R. C. (2020) “The method of finite spheres in acoustic wave propagation through nonhomogeneous media: Inf-sup stability conditions”, Vietnam Journal of Mechanics. Hanoi, Vietnam, 42(3), pp. 209–237. doi: 10.15625/0866-7136/15336.