HOUSTON, Kevin. On Singularities of Folding Maps and Augmentations. Mathematica Scandinavica, Berkeley, CA, United States, v. 82, n. 2, p. 191–206, 1998. DOI: 10.7146/math.scand.a-13833. Disponível em: https://journals.msp.org/mscand/article/view/995. Acesso em: 25 jul. 2026.