DOUGLASS, S. A. On a Concept of Summability in Amenable Groups. MATHEMATICA SCANDINAVICA, [S. l.], v. 23, p. 96–102, 1968. DOI: 10.7146/math.scand.a-10900. Disponível em: https://www.mscand.dk/article/view/10900. Acesso em: 14 apr. 2025.