FOLNER, E. Note on a generalization of a theorem of Bogolioùboff. MATHEMATICA SCANDINAVICA, [S. l.], v. 2, p. 223–225, 1954. DOI: 10.7146/math.scand.a-10408. Disponível em: https://www.mscand.dk/article/view/10408. Acesso em: 1 may. 2024.