BATTY, Charles J. K.; ROBINSON, Derek W. Commutators and generators. MATHEMATICA SCANDINAVICA, [S. l.], v. 62, p. 303–326, 1988. DOI: 10.7146/math.scand.a-12220. Disponível em: https://www.mscand.dk/article/view/12220. Acesso em: 5 dec. 2025.