Lagno VI, Spichak SV. Group classification of quasilinear elliptic-type equations. II. Invariance under solvable Lie algebras. Ukr. Mat. Zhurn. [Internet]. 2011Feb.25 [cited 2024Apr.28];63(2):200-15. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/2711