HUSTAD, O. Extension of Positve Linear Functionals. MATHEMATICA SCANDINAVICA, [S. l.], v. 11, p. 63–78, 1962. DOI: 10.7146/math.scand.a-10650. Disponível em: https://www.mscand.dk/article/view/10650. Acesso em: 5 may. 2024.