HAAGERUP, Uffe; KADISON, Richard V.; PEDERSEN, Gert K. Means of unitary operators, revisited. MATHEMATICA SCANDINAVICA, [S. l.], v. 100, n. 2, p. 193–197, 2007. DOI: 10.7146/math.scand.a-15021. Disponível em: https://tidsskrift.dk/math/article/view/15021. Acesso em: 14 aug. 2026.