1. A. Vilenkin, Phys. Rev. D27, 2848 (1983).
2. A. A. Starobinsky, in Current Topics in Field Theory, Quantum Gravity and
Strings, Lecture Notes in Physics 206, eds H. J. de Vega and N. Sanchez (Springer Verlag), p. 107.
3. A. D. Linde, Phys. Lett. B175, 395–400 (1986).
4. A. S. Goncharov, A. D. Linde and V. F. Mukhanov, Int. J. Mod. Phys. A2, 561–591 (1987).
5. A. Vilenkin and L. H. Ford, Phys. Rev. D26, 1231 (1982).