NETESOVA, T. M. Group analysis of boundary-value problems of mathematical physics. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 51, n. 1, p. 140–144, 1999. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4593. Acesso em: 5 dec. 2025.