BRASCHE, J. F.; KOSHMANENKO, V. D.; NEIDHARDT, H. New aspects of Krein’s extension theory. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 46, n. 1-2, p. 37–54, 1994. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5768. Acesso em: 14 apr. 2025.