FANG, J.; HADWIN, D.; MA, X. On spectra and Brown’s spectral measures of elements in free products of matrix algebras. MATHEMATICA SCANDINAVICA, [S. l.], v. 103, n. 1, p. 77–96, 2008. DOI: 10.7146/math.scand.a-15070. Disponível em: https://www.mscand.dk/article/view/15070. Acesso em: 3 may. 2024.