Books:
Lee, J. M.: Riemannian Manifolds: An Introduction to Curvature. Graduate Texts in Mathematics, 176. Springer-Verlag, 1997
Gallot, S., Hulin, D., Lafontaine, J.: Riemannian Geometry. Springer. 2nd edition, 1993
Jost, J.: Riemannian Geometry and Geometric Analysis 5th edition. Springer-Verlag, 2008
Petersen, P.: Riemannian Geometry Graduate Texts in Mathematics, 171. Springer-Verlag, 1998
Kobayashi, S., Nomizu, K.: Foundations of Differential Geometry
do Carmo, M: Riemannian Geometry. Birkhäuser, Boston, MA, 1992