Averaging the AGN X-ray spectra from deep Chandra fields S. Falocco, F. J. Carrera, A. Corral, E. Laird, K. Nandra, X. Barcons, M. J. Page and J. Digby-North A&A, 538 (2012) A83 Published online: 09 February 2012 DOI: 10.1051/0004-6361/201117965