KLYUS, I. S.; PTASHNIK, B. I. A multipoint problem for partial differential equations unresolved with respect to the higher time derivative. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 51, n. 12, p. 1604–1613, 1999. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4765. Acesso em: 5 dec. 2025.