BRUCE, J.; GIBLIN, P.; TARI, F. Families of surfaces: Height functions and projections to planes. MATHEMATICA SCANDINAVICA, [S. l.], v. 82, n. 2, p. 165–185, 1998. DOI: 10.7146/math.scand.a-13831. Disponível em: https://www.mscand.dk/article/view/13831. Acesso em: 27 apr. 2024.