PACKER, Judith A. Twisted group $C^*$-algebras corresponding to nilpotent discrete groups. Mathematica Scandinavica, Berkeley, CA, United States, v. 64, p. 109–122, 1989. DOI: 10.7146/math.scand.a-12250. Disponível em: https://journals.msp.org/mscand/article/view/1399. Acesso em: 24 jul. 2026.