ÖZEN, K. Green’s functional for higher-order ordinary differential equations with general nonlocal conditions and variable principal coefficient. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 71, n. 1, p. 99–116, 2019. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1422. Acesso em: 5 dec. 2025.