ELLIOT, George A.; TAKEMOTO, Hideo. On $C^*$-algebra extensions relative to a factor of type $\mathrm{II}_\infty$. Mathematica Scandinavica, Berkeley, CA, United States, v. 53, p. 245–255, 1983. DOI: 10.7146/math.scand.a-12032. Disponível em: https://journals.msp.org/mscand/article/view/1637. Acesso em: 25 jul. 2026.