KADISON, Richard V.; PEDERSEN, Gert K. Means and convex combinations of unitary operators. Mathematica Scandinavica, Berkeley, CA, United States, v. 57, p. 249–266, 1985. DOI: 10.7146/math.scand.a-12116. Disponível em: https://journals.msp.org/mscand/article/view/1552. Acesso em: 25 jul. 2026.