Comments to the review "Nonthermal phenomena in clusters of galaxies" by   Y.Rephaeli et al. that will appear on the book: Clusters of galaxies: beyond   the thermal view
  Comments to the review "Nonthermal Phenomena in Clusters of Galaxies" by Y.Rephaeli et al. (arXiv:0801.0982 [astro-ph]) that regard the presence of a hard X-ray excess in the Coma cluster, A2199, A2163 and the Bullet cluster. 
Roberto Fusco-Femiano and Mauro Orlandini