HANSEN, Lundsgaard Vagn. Some Theorems on Direct Limits of Expanding Sequences of Manifolds. Mathematica Scandinavica, Berkeley, CA, United States, v. 29, p. 5–36, 1971. DOI: 10.7146/math.scand.a-11031. Disponível em: https://journals.msp.org/mscand/article/view/2323. Acesso em: 25 jul. 2026.