LAGNO, V. I.; SPICHAK, S. V. Group classification of quasilinear elliptic-type equations. II. Invariance under solvable Lie algebras. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 63, n. 2, p. 200–215, 2011. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2711. Acesso em: 5 dec. 2025.