Reconstruction of the primordial fluctuation spectrum from the five-year   WMAP data by the cosmic inversion method with band-power decorrelation   analysis
  The primordial curvature fluctuation spectrum is reconstructed by the cosmic inversion method using the five-year WMAP data of the cosmic microwave background temperature anisotropy. We apply the covariance matrix analysis and decompose the reconstructed spectrum into statistically independent band-powers. The statistically significant deviation from a simple power-law spectrum suggested by the analysis of the first-year data is not found in the five-year data except possibly at one point near the border of the wavenumber domain where accurate reconstruction is possible. 
Ryo Nagata and Jun'ichi Yokoyama