J. Zibin. (2008)cite arxiv:0804.1787
Comment: 16 pages, 3 figures; numerical results and discussion expanded, one
figure added; version accepted to Phys. Rev. D.
N. Brouzakis, N. Tetradis, and E. Tzavara. (2007)cite arxiv:astro-ph/0703586
Comment: 27 pages, 9 figures, revised version to appear in JCAP, analytical
estimate included, typos corrected.