1. A. Einstein and M. Grossmann, Z. Math. and Phys. 62, 225–261 (1913).
2. A. L. Zelmanov and V. G. Agakov, The Elements of General Relativity (Nauka, Moscow, 1989) [in Russian].
3. A. Einstein, Akad. Wiss. 48(2), 844–847 (1915).
4. R. R. Feynman, F. B. Moringo, and W. G. Wagner, Feynman Lectures on Gravitation, Ed. by Brian Hatfield (Reading, Mass., Addison-Wesley, 1995).
5. K. Schwarzschild, Akad. Wiss. 48, 189–196 (1916).