SKAU, Christian F. Positive self-adjoint extensions of operators affiliated with a von Neumann algebra. Mathematica Scandinavica, Berkeley, CA, United States, v. 44, p. 171–195, 1979. DOI: 10.7146/math.scand.a-11801. Disponível em: https://journals.msp.org/mscand/article/view/1848. Acesso em: 25 jul. 2026.