SEIFERT, B. G. Classification of fibred group extensions and $H^1$. Mathematica Scandinavica, Berkeley, CA, United States, v. 58, p. 105–113, 1986. DOI: 10.7146/math.scand.a-12132. Disponível em: https://journals.msp.org/mscand/article/view/1496. Acesso em: 25 jul. 2026.