PIKUTA, P. On sets of constant distance from a planar set. Topological Methods in Nonlinear Analysis, [S. l.], v. 21, n. 2, p. 369–374, 2003. Disponível em: https://apcz.umk.pl/TMNA/article/view/TMNA.2003.022. Acesso em: 27 apr. 2024.