BUSEMANN, H.; PEDERSEN, F. P. Tori with one-parameter groups of motions. MATHEMATICA SCANDINAVICA, [S. l.], v. 3, p. 209–220, 1955. DOI: 10.7146/math.scand.a-10438. Disponível em: https://www.mscand.dk/article/view/10438. Acesso em: 3 may. 2024.