J. Silk, и G. Mamon. (2012)cite arxiv:1207.3080Comment: To appear in "Frontiers in Astrophysics ", a special issue of the international journal "Research in Astronomy and Astrophysics", commissioned by the Executive Committee of the International Astronomical Union and to be distributed at the IAU XXVIIIth General Assembly (30 pages, 32 figures, 192 references). Comments welcome to both silk AAT iap.fr and gam AAT iap.fr.