HOBBS, C. A.; KIRK, N. P. On the classification and bifurcation of multigerms of maps from surfaces to 3-space. Mathematica Scandinavica, Berkeley, CA, United States, v. 89, n. 1, p. 57–96, 2001. DOI: 10.7146/math.scand.a-14331. Disponível em: https://journals.msp.org/mscand/article/view/874. Acesso em: 24 jul. 2026.