DMYTRYSHYN, M.I.; LOPUSHANSKY, O.V. Spectral approximations of strongly degenerate elliptic differential operators. Carpathian Mathematical Publications, [S. l.], v. 11, n. 1, p. 48–53, 2019. DOI: 10.15330/cmp.11.1.48-53. Disponível em: https://scijournals.pnu.edu.ua/index.php/cmp/article/view/1507. Acesso em: 28 apr. 2024.