FOSSUM, R.; FOXBY, H. -b. The Category of Graded Modules. Mathematica Scandinavica, Berkeley, CA, United States, v. 35, p. 288–300, 1974. DOI: 10.7146/math.scand.a-11553. Disponível em: https://journals.msp.org/mscand/article/view/2092. Acesso em: 25 jul. 2026.