HOLE, Arne. Invariant Differential Operators and Polynomials of Lie Transformation Groups. MATHEMATICA SCANDINAVICA, [S. l.], v. 34, p. 109–123, 1974. DOI: 10.7146/math.scand.a-11511. Disponível em: https://tidsskrift.dk/math/article/view/11511. Acesso em: 14 aug. 2026.