SJÖDIN, Gunnar. On Filtered Modules and their Associated Graded Modules. Mathematica Scandinavica, Berkeley, CA, United States, v. 33, p. 229–249, 1973. DOI: 10.7146/math.scand.a-11486. Disponível em: https://journals.msp.org/mscand/article/view/2177. Acesso em: 25 jul. 2026.