PTASHNYK, B.; REPETYLO, S. The Dirichlet–Neumann problem for linear nonelliptic partial differential equations with constant coefficients . Reports of the National Academy of Sciences of Ukraine, Kyiv, Ukraine, n. 2, p. 24–31, 2025. DOI: 10.15407/dopovidi2015.02.024. Disponível em: https://nasu-periodicals.org.ua/index.php/dp/article/view/13369. Acesso em: 10 jan. 2025.