Geometrically finite groups, Patterson-Sullivan measures and Ratner's rigidity theorem. L. Flaminio; R.J. Spatzier — 1990 Inventiones mathematicae
Some examples of higher rank manifolds of nonnegative curvature. M. Strake; R.J. Spatzier — 1990 Commentarii mathematici Helvetici
Nonstationary normal forms and rigidity of group actions. Katok, A.; Spatzier, R.J. — 1996 Electronic Research Announcements of the American Mathematical Society [electronic only]