WILS, W. Direct Integrals of Hilbert Spaces I. MATHEMATICA SCANDINAVICA, [S. l.], v. 26, p. 73–88, 1970. DOI: 10.7146/math.scand.a-10967. Disponível em: https://www.mscand.dk/article/view/10967. Acesso em: 9 may. 2024.