JACOBSSON, Calle. On the double Poincaré series of the enveloping algebras of certain graded Lie algebras. Mathematica Scandinavica, Berkeley, CA, United States, v. 51, p. 45–58, 1982. DOI: 10.7146/math.scand.a-11963. Disponível em: https://journals.msp.org/mscand/article/view/1684. Acesso em: 25 jul. 2026.