RAEBURN, Iain; SINCLAIR, Allan M. The $C^*$-algebra generated by two projections. Mathematica Scandinavica, Berkeley, CA, United States, v. 65, p. 278–290, 1989. DOI: 10.7146/math.scand.a-12283. Disponível em: https://journals.msp.org/mscand/article/view/1364. Acesso em: 24 jul. 2026.