ROBINSON, Derek W. Commutators and generators II. Mathematica Scandinavica, Berkeley, CA, United States, v. 64, p. 87–108, 1989. DOI: 10.7146/math.scand.a-12249. Disponível em: https://journals.msp.org/mscand/article/view/1400. Acesso em: 24 jul. 2026.