LAURSEN, Kjeld B.; SINCLAIR, Allan M. Lifting matrix units in $C^*$-algebras II. Mathematica Scandinavica, Berkeley, CA, United States, v. 37, p. 167–172, 1975. DOI: 10.7146/math.scand.a-11598. Disponível em: https://journals.msp.org/mscand/article/view/2078. Acesso em: 25 jul. 2026.