HOPENWASSER, Alan. Isometries on Irreducible Triangular Operator Algebras. Mathematica Scandinavica, Berkeley, CA, United States, v. 30, p. 136–140, 1972. DOI: 10.7146/math.scand.a-11069. Disponível em: https://journals.msp.org/mscand/article/view/2254. Acesso em: 25 jul. 2026.