OLUBUMMO, A. Finitely Additive Measures on the Non-Negative Integers. Mathematica Scandinavica, Berkeley, CA, United States, v. 24, p. 186–194, 1969. DOI: 10.7146/math.scand.a-10929. Disponível em: https://journals.msp.org/mscand/article/view/2373. Acesso em: 25 jul. 2026.