Revealing X-ray obscured quasars in SWIRE sources with extreme mid-IR/optical flux ratiosG. Lanzuisi, E. Piconcelli, F. Fiore, C. Feruglio, C. Vignali, M. Salvato and C. GruppioniA&A, 498 1 (2009) 67-81DOI: https://doi.org/10.1051/0004-6361/200811282
