LukovskyI. O., and TimokhaA. N. “Variational Formulations of Nonlinear Boundary-Value Problems With a Free Boundary in the Theory of Interaction of Surface Waves With Acoustic Fields”. Ukrains’kyi Matematychnyi Zhurnal 45, no. 12 (December 25, 1993): 1642–1652. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5972.