WATTENBERG, F. Differentiable Motions of Unknotted, Unlinked Circles in 3-Space. MATHEMATICA SCANDINAVICA, [S. l.], v. 30, p. 107–135, 1972. DOI: 10.7146/math.scand.a-11068. Disponível em: https://www.mscand.dk/article/view/11068. Acesso em: 30 apr. 2024.