FUSHCHICH , W. I.; ZHDANOV , R. Z. Conditional symmetry and reduction of differential equations with partial derivatives . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 44, n. 7, p. 970–982, 1992. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8129. Acesso em: 14 apr. 2025.