YAKOVETS, V. P. On the structure of the general solution of a degenerate linear system of second-order differential equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 50, n. 2, p. 292–298, 1998. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4962. Acesso em: 17 apr. 2025.