A General Character Formula for Irreducible Projections on L2 of a Nilmanifold. Frederick P. Greenleaf; Lawrence Corwin; Richard Penney — 1977 Mathematische Annalen
Automorphisms, Orbits, and Homogeneous Spaces of Non-Connected Lie Groups. Frederick P. Greenleaf; Martin Moskowitz; Linda Preiss-Rothschild — 1974 Mathematische Annalen