KLYUCHNYK, I. H. Linear system of differential equations with turning point. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 62, n. 5, p. 625–642, 2010. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2893. Acesso em: 5 dec. 2025.