PERLES, M. A.; SHEPARD, G. C. Angle Sums of Convex Polytopes. MATHEMATICA SCANDINAVICA, [S. l.], v. 21, p. 199–218, 1967. DOI: 10.7146/math.scand.a-10860. Disponível em: https://www.mscand.dk/article/view/10860. Acesso em: 30 apr. 2024.