NIELSEN, Ole A. The failure of the topological Frobenius property for nilpotent Lie groups. Mathematica Scandinavica, Berkeley, CA, United States, v. 45, p. 305–310, 1979. DOI: 10.7146/math.scand.a-11845. Disponível em: https://journals.msp.org/mscand/article/view/1801. Acesso em: 25 jul. 2026.