The critical case for singularly perturbed Noether boundary-value problems. Neliniini Kolyvannya, [S. l.], v. 11, n. 1, p. 45–54, 2008. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/461. Acesso em: 21 jan. 2026.