PALMÉR, Ingegerd. The global homological dimension of semi-trival extensions of rings. Mathematica Scandinavica, Berkeley, CA, United States, v. 37, p. 223–256, 1975. DOI: 10.7146/math.scand.a-11603. Disponível em: https://journals.msp.org/mscand/article/view/2065. Acesso em: 25 jul. 2026.