MAZKO, A. G. Distribution of the spectrum and representation of solutions of degenerate dynamical systems. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 50, n. 7, p. 930–936, 1998. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4873. Acesso em: 5 dec. 2025.