RAIMI, Ralph A. On a Theorem of E. Folner. MATHEMATICA SCANDINAVICA, [S. l.], v. 6, p. 47–49, 1958. DOI: 10.7146/math.scand.a-10535. Disponível em: https://www.mscand.dk/article/view/10535. Acesso em: 5 dec. 2025.