PTASHNIK, B. I.; SYLYUHA, L. P. Multipoint problem for typeless factorized differential operators. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 48, n. 1, p. 66–79, 1996. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5364. Acesso em: 14 apr. 2025.