BAVULA , V. V. Simple $D [X, Y; \sigma, а]$-modules . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 44, n. 12, p. 1628–1644, 1992. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8189. Acesso em: 5 dec. 2025.