1. É. Cartan, Geometry of Riemannian Spaces (Math. Sci. Press, Boston, 1983; Gostekhizdat, Moscow, 1936).
2. É._G. Poznyak and E. V. Shikin, Differential Geometry: The First Acquaintance (Izd. Moskov. Univ., Moscow, 1990) [in Russian].
3. J. M. Lee, Riemannian Manifolds. An Introduction to Curvature, in Grad. Texts in Math. (Springer, New York, 1997), Vol. 176.
4. P. K. Rashevskii, Riemannian Geometry and Tensor Analysis (Gos. Izd. Tekhn.-Teor. Lit., Moscow, 1953) [in Russian].
5. F. R. Gantmacher, The Theory of Matrices (Chelsea, New York, 1959; Nauka, Moscow, 1988).