HAKL, R. Periodic boundary-value problem for third-order linear functional differential equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 60, n. 3, p. 413–425, 2008. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3164. Acesso em: 27 apr. 2025.