GOI, T. P.; PTASHNIK, B. I. Problem with nonlocal conditions for weakly nonlinear hyperbolic equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 49, n. 2, p. 186–195, 1997. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4996. Acesso em: 6 dec. 2025.