LÖFWALL, Clas. Appendix to "On the double Poincaré series of the enveloping algebras of certain graded Lie algebras". MATHEMATICA SCANDINAVICA, [S. l.], v. 51, p. 59–62, 1982. DOI: 10.7146/math.scand.a-11964. Disponível em: https://tidsskrift.dk/math/article/view/11964. Acesso em: 14 aug. 2026.