VLASII, O. D.; PTASHNIK, B. I. A Problem with Nonlocal Conditions for Partial Differential Equations Unsolved with Respect to the Leading Derivative. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 55, n. 8, p. 1022–1034, 2003. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3978. Acesso em: 5 dec. 2025.