HUSTAD, O. Linear Inequalities and Positive Extension of Linear Functionals. MATHEMATICA SCANDINAVICA, [S. l.], v. 8, p. 333–338, 1960. DOI: 10.7146/math.scand.a-10615. Disponível em: https://www.mscand.dk/article/view/10615. Acesso em: 5 may. 2024.