SCHERK, Peter. On Sets of Vectors. Mathematica Scandinavica, Berkeley, CA, United States, v. 16, p. 38–40, 1965. DOI: 10.7146/math.scand.a-10746. Disponível em: https://journals.msp.org/mscand/article/view/2573. Acesso em: 25 jul. 2026.