LI, Ming; SUGAWA, Toshiyuki. Some extensions of the Open Door Lemma. Studia Universitatis Babeș-Bolyai Mathematica, [S. l.], v. 60, n. 3, p. 421–430, 2015. Disponível em: https://studia.reviste.ubbcluj.ro/index.php/subbmathematica/article/view/5793. Acesso em: 5 feb. 2025.