1. J. A. Wheeler,Int. J. Theor. Phys. 21, 557 (1982).
2. C. W. Misner, K. S. Thorne, and J. A. Wheeler,Gravitation (Freeman, San Francisco, 1970).
3. A. Yasuhara,Recursive Function Theory and Logic (Academic Press, New York, 1971).
4. G. Faltings,Invent. Math. 73, 349 (1983).
5. Int. J. Theor. Phys. 21, Nos. 3–4 (1982).