PACKER, Judith A. Twisted group $C^*$-algebras corresponding to nilpotent discrete groups. MATHEMATICA SCANDINAVICA, [S. l.], v. 64, p. 109–122, 1989. DOI: 10.7146/math.scand.a-12250. Disponível em: https://tidsskrift.dk/math/article/view/12250. Acesso em: 14 aug. 2026.