Conditions of appearing solutions of linear weakly perturbed finite-difference boundary problems. Neliniini Kolyvannya, [S. l.], v. 1, n. 2, p. 118–121, 1998. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/27. Acesso em: 22 jan. 2026.