HOLE, A. 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://www.mscand.dk/article/view/11511. Acesso em: 8 may. 2024.