Partial Differential Operators and Discrete Subgroups of a Lie Group. Palle E.T. Jorgensen (1980) Mathematische Annalen
Picard-Lefschetz theory and characters of a semisimple Lie group. W. Rossmann (1995) Inventiones mathematicae
Picard-Lefschetz theory for the coadjoint quotient of a semisimple Lie algebra. W. Rossmann (1995) Inventiones mathematicae
Projections of Orbits and Asymptotic Behavior of Multiplicities for Compact Connected Lie Groups. G.J. Heckman (1982) Inventiones mathematicae