ŠENKYŘÍK, Martin. Periodic solutions of a second order differential equation with discontinuities in the spatial variable. Topological Methods in Nonlinear Analysis, [S. l.], v. 6, n. 1, p. 199–206, 1995. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1995.041. Acesso em: 20 may. 2025.