SAKHNOVICH, L. A. Spectral problems for canonical systems of finite-difference equations on an axis. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 49, n. 6, p. 779–788, 1997. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5062. Acesso em: 14 apr. 2025.