BOLAÑOS, G.; DE LA PEÑA, J. A. Algebras with vanishing $\mathrm{Ext}^2\ (X,X)$. Mathematica Scandinavica, Berkeley, CA, United States, v. 83, n. 2, p. 177–191, 1998. DOI: 10.7146/math.scand.a-13849. Disponível em: https://journals.msp.org/mscand/article/view/979. Acesso em: 25 jul. 2026.