MYKYTYUK, Ya. V.; HRYNIV, R. O. 1-D Schrödinger operators with periodic singular potentials. Methods of Functional Analysis and Topology, [S. l.], v. 7, n. 4, p. 31–42, 2001. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/164. Acesso em: 19 dec. 2025.