1. Gibbons, S.W., Hawking, S.W.: Cosmological event horizons, thermodynamics and particle creation. DAMTP, University of Cambridge, preprint
2. Hartle, J., Hawking, S.W.: Path integral derivation of black hole radiance. Cal. Tech. Orange Aid preprint
3. To be published
4. Taub, A.: Ann. Math.53, 472 (1951)
5. Newman, E., Tamburino, L., Unti, T.: JMP4, 915 (1963)