Manifolds of nonpositive curvature and their buildings Keith Burns; Ralf Spatzier — 1987 Publications Mathématiques de l'IHÉS
On topological Tits buildings and their classification Keith Burns; Ralf Spatzier — 1987 Publications Mathématiques de l'IHÉS
Smooth classification of Cartan actions of higher rank semisimple Lie groups and their lattices. Goetze, Edward R.; Spatzier, Ralf J. — 1999 Annals of Mathematics. Second Series