JENSEN, A.; JONDRUP, S. Smash products, group actions and group graded rings. MATHEMATICA SCANDINAVICA, [S. l.], v. 68, p. 161–170, 1991. DOI: 10.7146/math.scand.a-12353. Disponível em: https://www.mscand.dk/article/view/12353. Acesso em: 28 apr. 2024.