HU, Shanwen; LIN, Huaxin; XUE, Yifeng. The tracial topological rank of extensions of $C^*$-algebras. Mathematica Scandinavica, Berkeley, CA, United States, v. 94, n. 1, p. 125–147, 2004. DOI: 10.7146/math.scand.a-14433. Disponível em: https://journals.msp.org/mscand/article/view/786. Acesso em: 24 jul. 2026.