1. V. A. Ambartsumyan, Problems of Modern Cosmology [in Russian], Moscow (1972).
2. V. L. Ginzburg, Gravitation. Problems and Perspectives [in Russian], Moscow (1972).
3. P. Jordan, Z. Physik 157, 112 (1959).
4. C. Brans and R. Dicke, Phys. Rev. 124, 925 (1961).
5. C. Will, Theory and Experiment in Gravitational Physics [Russian translation], Gosatomizdat (1985).