Is MgIIλ2800 a reliable virial broadening estimator for quasars? P. Marziani, J. W. Sulentic, I. Plauchu-Frayn and A. del Olmo A&A, 555 (2013) A89 Published online: 05 July 2013 DOI: 10.1051/0004-6361/201321374