WEBER, J. Classical Morse theory revisited - I backward $\lambda$-lemma and homotopy type. Topological Methods in Nonlinear Analysis, [S. l.], v. 47, n. 2, p. 641–646, 2016. DOI: 10.12775/TMNA.2016.020. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2016.020. Acesso em: 28 mar. 2024.