HENDERSON, Johnny; LUCA, Rodica. Positive solutions for singular systems of higher-order multi-point boundary value problems. Mathematical Modelling and Analysis, [S. l.], v. 18, n. 3, p. 309–324, 2013. DOI: 10.3846/13926292.2013.804009. Disponível em: https://journals.vilniustech.lt/index.php/MMA/article/view/4115. Acesso em: 19 may. 2025.