1. B. S. DeWitt andR. W. Brehme:Ann. of Phys.,9, 220 (1960).
2. H. Nariai andT. Kimura:Prog. Theor. Phys.,29, 296, 915 (1963);31, 1138 (1964).
3. R. Arnowitt, S. Deser andC. W. Misner: inGravitation: An Introduction to Current Research, edited byL. Witten (New York, N. Y., 1962), p. 227.
4. L. Parker:Phys. Rev.,183, 1057 (1969);Phys. Rev. D,3, 346 (1971).
5. Ya. B. Zel’Dovich andA. A. Starobinskii:Sov. Phys. JETP,34, 1159 (1972).