INGELSTAM, Lars. A Vertex Property for Banach Algebras with Identity. Mathematica Scandinavica, Berkeley, CA, United States, v. 11, p. 22–32, 1962. DOI: 10.7146/math.scand.a-10646. Disponível em: https://journals.msp.org/mscand/article/view/2700. Acesso em: 25 jul. 2026.