ZABAVSKII, B. V. A noncommutattve analog of the cohen theorem. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 48, n. 5, p. 707–710, 1996. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5304. Acesso em: 5 dec. 2025.