GÓRNIEWICZ, L.; NISTRI, P. Topological essentiality and nonlinear boundary value control problems$^*$. Topological Methods in Nonlinear Analysis, [S. l.], v. 13, n. 1, p. 53–72, 1999. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.1999.003. Acesso em: 22 jul. 2024.