CASSIER, Gilles; SUCIU, Nicolae. Sharpened forms of a von Neumann inequality for $\rho$-contractions. MATHEMATICA SCANDINAVICA, [S. l.], v. 102, n. 2, p. 265–282, 2008. DOI: 10.7146/math.scand.a-15062. Disponível em: https://tidsskrift.dk/math/article/view/15062. Acesso em: 14 aug. 2026.