HELGASON, Sigurdur. A characterization of the intersection of $L^1$-spaces. MATHEMATICA SCANDINAVICA, [S. l.], v. 4, p. 5–8, 1956. DOI: 10.7146/math.scand.a-10450. Disponível em: https://tidsskrift.dk/math/article/view/10450. Acesso em: 13 aug. 2026.