AndrusyakR. V., Burdeina N. O., and KirilichV. M. 2009. “Classical Solvability of a Problem With Moving Boundaries for a Hyperbolic System of Quasilinear Equations”. Ukrains’kyi Matematychnyi Zhurnal 61 (7), 867-91. https://umj.imath.kiev.ua/index.php/umj/article/view/3064.