FABRICIUS-BJERRE, F. On the Double Tangents of Plane Closed Curves. MATHEMATICA SCANDINAVICA, [S. l.], v. 11, p. 113–116, 1962. DOI: 10.7146/math.scand.a-10656. Disponível em: https://www.mscand.dk/article/view/10656. Acesso em: 27 apr. 2024.