Dust covering factor, silicate emission, and star formation in luminous QSOsR. Maiolino, O. Shemmer, M. Imanishi, H. Netzer, E. Oliva, D. Lutz and E. SturmA&A, 468 3 (2007) 979-992DOI: https://doi.org/10.1051/0004-6361:20077252