PTASHNIK, B. I.; REPETYLO, S. M. Boundary-value problem with mixed conditions for linear typeless partial differential equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 68, n. 5, p. 665–682, 2016. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1870. Acesso em: 5 dec. 2025.