ELLIS, A. J. On Partial Orderings of Normed Spaces. MATHEMATICA SCANDINAVICA, [S. l.], v. 23, p. 123–132, 1968. DOI: 10.7146/math.scand.a-10903. Disponível em: https://tidsskrift.dk/math/article/view/10903. Acesso em: 13 aug. 2026.