NIELSEN, Jens P. Cohomology of some non-selfadjoint operator algebras. Mathematica Scandinavica, Berkeley, CA, United States, v. 47, p. 150–156, 1980. DOI: 10.7146/math.scand.a-11881. Disponível em: https://journals.msp.org/mscand/article/view/1769. Acesso em: 25 jul. 2026.