NAMIOKA, I. Folner’s Conditions for Amenable Semi-Groups. Mathematica Scandinavica, Berkeley, CA, United States, v. 15, p. 18–28, 1964. DOI: 10.7146/math.scand.a-10723. Disponível em: https://journals.msp.org/mscand/article/view/2623. Acesso em: 25 jul. 2026.