Existence of Positive Solutions for a Nonlinear Second Order Periodic Boundary Value Problem. Journal of Nonlinear Modeling and Analysis, [S. l.], v. 2, n. 4, p. 513–524, 2024. DOI: 10.12150/jnma.2020.513. Disponível em: https://global-sci.com/index.php/jnma/article/view/13574. Acesso em: 6 dec. 2025.