Ionization by early quasars and Cosmic Microwave Background   anisotropies. (Erratum)
  The y axis of figure 9, which gives the power amplitude ($l(l+1)C_l$) in units of $10^{-12}$, is incorrectly reported. The correct values are obtained by dividing the amplitudes by 16. All the relative values remain valid, and this therefore does not change the conclusions of the paper. 
N. Aghanim (IAS, Orsay), F.-X. D\'esert (Obs. Grenoble), J.-L. Puget   (IAS, Orsay) & R. Gispert (IAS, Orsay)