HOFF, Georges. Cohomologies et extensions de catégories. Mathematica Scandinavica, Berkeley, CA, United States, v. 74, p. 191–207, 1994. DOI: 10.7146/math.scand.a-12489. Disponível em: https://journals.msp.org/mscand/article/view/1136. Acesso em: 25 jul. 2026.