WEIBULL, Thomas. A natural map from the ext Künneth sequence to the Tor one. Mathematica Scandinavica, Berkeley, CA, United States, v. 53, p. 203–206, 1983. DOI: 10.7146/math.scand.a-12027. Disponível em: https://journals.msp.org/mscand/article/view/1644. Acesso em: 25 jul. 2026.