HAVNEN, Johan. Completely Monotonic Functions on $n$-Dimensional Lattices. Mathematica Scandinavica, Berkeley, CA, United States, v. 33, p. 314–322, 1973. DOI: 10.7146/math.scand.a-11493. Disponível em: https://journals.msp.org/mscand/article/view/2174. Acesso em: 25 jul. 2026.