HENDERSON, Johnny; KOSMATOV, Nickolai. Positive Solutions of the Semipositone Neumann Boundary Value Problem. Mathematical Modelling and Analysis, [S. l.], v. 20, n. 5, p. 578–584, 2015. DOI: 10.3846/13926292.2015.1087435. Disponível em: https://journals.vilniustech.lt/index.php/MMA/article/view/1020. Acesso em: 28 may. 2025.