PRISHLYAK, O. O. Vector fields with a given set of singular points. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 49, n. 10, p. 1373–1384, 1997. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5135. Acesso em: 5 dec. 2025.