GOODARZI, K. .; NADJAFIKHAH *, M. . λ-Symmetry and Integrating Factor For x ̈(f(t,x)+g(t,x)x ̇)e^x: Mathematics, Symmetry. Hyperscience International Journal, [S. l.], v. 2, n. 1, p. 7–13, 2022. DOI: 10.55672/hij2022pp7-13. Disponível em: https://hscience.org/index.php/hij/article/view/14. Acesso em: 19 jul. 2024.