GIERTZ, M. A Note on a Problem of Busemann. Mathematica Scandinavica, Berkeley, CA, United States, v. 25, p. 145–148, 1969. DOI: 10.7146/math.scand.a-10951. Disponível em: https://journals.msp.org/mscand/article/view/2390. Acesso em: 25 jul. 2026.