HAVNEN, J. Completely Monotonic Functions on $n$-Dimensional Lattices. MATHEMATICA SCANDINAVICA, [S. l.], v. 33, p. 314–322, 1973. DOI: 10.7146/math.scand.a-11493. Disponível em: https://www.mscand.dk/article/view/11493. Acesso em: 8 may. 2024.