HAAGERUP, Uffe; KADISON, Richard V.; PEDERSEN, Gert K. Means of unitary operators, revisited. Mathematica Scandinavica, Berkeley, CA, United States, v. 100, n. 2, p. 193–197, 2007. DOI: 10.7146/math.scand.a-15021. Disponível em: https://journals.msp.org/mscand/article/view/676. Acesso em: 24 jul. 2026.