WALTHER, H.-O. Stable periodic motion of a delayed spring. Topological Methods in Nonlinear Analysis, [S. l.], v. 21, n. 1, p. 1–28, 2003. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2003.001. Acesso em: 22 jul. 2024.