KISELMAN, C. O. Smoothness of vector sums of plane convex sets. MATHEMATICA SCANDINAVICA, [S. l.], v. 60, p. 239–252, 1987. DOI: 10.7146/math.scand.a-12183. Disponível em: https://www.mscand.dk/article/view/12183. Acesso em: 29 mar. 2024.