LAURSEN, K. B. A Note on Lifting of Matrix Units in $C^*$-Algebras. MATHEMATICA SCANDINAVICA, [S. l.], v. 33, p. 338–342, 1973. DOI: 10.7146/math.scand.a-11495. Disponível em: https://www.mscand.dk/article/view/11495. Acesso em: 6 may. 2024.