CASSIER, Gilles; SUCIU, Nicolae. Sharpened forms of a von Neumann inequality for $\rho$-contractions. Mathematica Scandinavica, Berkeley, CA, United States, v. 102, n. 2, p. 265–282, 2008. DOI: 10.7146/math.scand.a-15062. Disponível em: https://journals.msp.org/mscand/article/view/635. Acesso em: 24 jul. 2026.