KLEPPE, Jan O. Deformations of graded algebras. Mathematica Scandinavica, Berkeley, CA, United States, v. 45, p. 205–231, 1979. DOI: 10.7146/math.scand.a-11837. Disponível em: https://journals.msp.org/mscand/article/view/1808. Acesso em: 25 jul. 2026.