MAWHIN, Jean. Parameter dependent pull-back of closed differential forms and invariant integrals. Topological Methods in Nonlinear Analysis, [S. l.], v. 26, n. 1, p. 17–33, 2005. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2005.023. Acesso em: 8 jul. 2025.