HELGASON, Sigurdur. A characterization of the intersection of $L^1$-spaces. Mathematica Scandinavica, Berkeley, CA, United States, v. 4, p. 5–8, 1956. DOI: 10.7146/math.scand.a-10450. Disponível em: https://journals.msp.org/mscand/article/view/2870. Acesso em: 25 jul. 2026.