Riemannian Geometry (Graduate Texts in Mathematics, 171) Peter Petersen
Differential Geometry and Symmetric Spaces (Pure & Applied Mathematics S.) Sigurdur Helgason
Riemannian Geometry: A Modern Introduction (Cambridge Studies in Advanced Mathematics, Series Number 98) Isaac Chavel
SPACES OF CONSTANT CURVATURE JOSEPH A. WOLF
Geometry of Nonpositively Curved Manifolds Patrick B. Eberlein