The Failure of the Topological Frobenius Property for Nilpotent Lie Groups. II. Ole A. Nielsen — 1981 Mathematische Annalen
The failure of the topological Frobenius property for nilpotent Lie groups. Ole A. Nielsen — 1979 Mathematica Scandinavica
A Fourier Transform for Compact Nilmanifolds with Flat Orbits. Ole A. Nielsen; Michael Rains — 1985 Mathematische Annalen