GRIMMER, Ronald; HE, Min. Fixed Point Theory and Nonlinear Periodic Systems. CUBO, A Mathematical Journal, [S. l.], v. 11, n. 3, p. 101–113, 2009. Disponível em: https://cubo.ufro.cl/index.php/cubo/article/view/1465. Acesso em: 12 oct. 2025.