ALDASHEV, S. A. Criterion for the Uniqueness of a Solution of the Darboux–Protter Problem for Degenerate Multidimensional Hyperbolic Equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 11, p. 1569–1575, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4024. Acesso em: 5 dec. 2025.