DONDÈ, T.; ZANOLIN, F. Multiple periodic solutions for one-sided sublinear systems: A refinement of the Poincaré-Birkhoff approach. Topological Methods in Nonlinear Analysis, [S. l.], v. 55, n. 2, p. 565–581, 2020. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2019.104. Acesso em: 29 mar. 2024.