The XMM-Newton view of IRAS 09104+4109: evidence for a changing-look Type 2 quasar? E. Piconcelli, F. Fiore, F. Nicastro, S. Mathur, M. Brusa, A. Comastri and S. Puccetti A&A, 473 1 (2007) 85-89 Published online: 16 July 2007 DOI: 10.1051/0004-6361:20077630