KARABASH, I. M. J-selfadjoint ordinary differential operators similar to selfadjoint operators. Methods of Functional Analysis and Topology, [S. l.], v. 6, n. 2, p. 22–49, 2000. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/116. Acesso em: 17 dec. 2025.