KHOMA, N. H. An exact solution of boundary-value problem. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 51, n. 8, p. 1142–1143, 1999. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4708. Acesso em: 5 dec. 2025.