NIELSEN, Ole A. The failure of the topological Frobenius property for nilpotent Lie groups. MATHEMATICA SCANDINAVICA, [S. l.], v. 45, p. 305–310, 1979. DOI: 10.7146/math.scand.a-11845. Disponível em: https://tidsskrift.dk/math/article/view/11845. Acesso em: 13 aug. 2026.