GONCALVES, Daciberg Lima. Generalized classes of groups, $C$-nilpotent spaces and "The Hurewicz theorem". Mathematica Scandinavica, Berkeley, CA, United States, v. 53, p. 39–61, 1983. DOI: 10.7146/math.scand.a-12015. Disponível em: https://journals.msp.org/mscand/article/view/1655. Acesso em: 25 jul. 2026.