SHISHANIN, O. E. Certain methods for construction of asymptotics for the Hill equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 44, n. 1, p. 142–145, 1992. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/7807. Acesso em: 6 dec. 2025.