1. M. M. Abdil’din, Mechanics of Einstein’s Gravitation Theory (Alma-Ata, 1988), 198 p. (in Russian).
2. V. A. Fock, Theory of Space, Time, and Gravity (Moscow, 1961), 563 p. (in Russian).
3. L. D. Landau and E.M. Lifshitz, Classical Field Theory (Moscow, 1973), 400 p. (in Russian).
4. B. Riemann, On the hypotheses that underlie geometry. In the book: “On the Basis of Geometry” (Gostekhizdat, Moscow, 1956), p. 325 (in Russian).
5. A. Livanova, Three Fates of World Cognition (Znanie, Moscow, 1969), p. 207 (in Russian).