RIBENBOIM, P. Pfister’s Dimension and the Level of Fields. Mathematica Scandinavica, Berkeley, CA, United States, v. 35, p. 301–308, 1974. DOI: 10.7146/math.scand.a-11554. Disponível em: https://journals.msp.org/mscand/article/view/2091. Acesso em: 25 jul. 2026.