On the use of photometric redshifts for X-ray selected AGNs S. Kitsionas, E. Hatziminaoglou, A. Georgakakis and I. Georgantopoulos A&A, 434 2 (2005) 475-482 Published online: 11 April 2005 DOI: 10.1051/0004-6361:20041916