BUDNYTS'KA, T. V.; PRISHLYAK, O. O. Equivalence of closed 1-forms on surfaces with edge. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 61, n. 11, p. 1455–1473, 2009. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3114. Acesso em: 27 apr. 2025.