BOMAN, Jan. Smoothness of sums of convex sets with real analytic boundaries. Mathematica Scandinavica, Berkeley, CA, United States, v. 66, p. 225–230, 1990. DOI: 10.7146/math.scand.a-12306. Disponível em: https://journals.msp.org/mscand/article/view/1318. Acesso em: 24 jul. 2026.