PIENE, Ragni. Courbes sur un trait et morphismes de contraction. MATHEMATICA SCANDINAVICA, [S. l.], v. 35, p. 5–15, 1974. DOI: 10.7146/math.scand.a-11528. Disponível em: https://www.mscand.dk/article/view/11528. Acesso em: 5 dec. 2025.