1. A. A. Grib, S. G. Mamaev, and V. M. Mostepanenko, Quantum Effects in Strong External Fields [in Russian], Atomizdat, Moscow (1980).
2. Cambridge Monogr. Math. Phys.;N. D. Birrell,1982
3. D. V. Gal’tsov, Particles and Fields in the Vicinity of Black Holes [in Russian], Moscow State Univ. Press, Moscow (1986).
4. Math. Its Appl. (Sov. Ser.);V. G. Bagrov,1990
5. V. G. Bagrov, M. C. Baldiotti, D. M. Gitman, and I. V. Shirokov, J. Math. Phys., 43, 2284–2305 (2002); arXiv:hep-th/0110037v3 (2001).