1. A. Sakharov, (1967). Dokl. Akad. Nauk SSSR 177, 70; Vacuum quantum fluctuations in curved space and the theory of gravitation, reprinted in (2000). Gen. Rel. Grav. 32, 365. See also the editor's note on that paper in H.-J. Schmidt, (2000). Gen. Rel. Grav. 32, 361.
2. S. Adler, (1982). Rev. Mod. Phys. 54, 729.
3. See, for example J. Hwang, H. Noh, (2000). Phys. Rev. D 61, 043511, Conserved cosmological structures in the one-loop superstring effective action (astro-ph/9909480); G. Ellis, D. Roberts, D. Solomons, and P. Dunsby, gr-qc/9912005, to appear in Phys. Rev. D.
4. H.-J. Schmidt, Comparing selfinteracting scalar fields and R + R 3 cosmological models, gr-qc/0106035, (1987). Astron. Nachr. 308, 183; H.-J. Schmidt, On the critical value of the curvature scalar, (1986). Proc. Conf. General Relativity GR 11, Stockholm, p. 117.
5. H.-J. Schmidt, New exact solutions for power-law inflation Friedmann models, gr-qc/0109004, (1990). Astron. Nachr. 311, 165; (1993). Gen. Rel. Grav. 25, 87, 863.