Estimating Black Hole Masses in Active Galactic Nuclei Using the Mg II λ2800 Emission Line - Wang, Jian-Guo; Dong, Xiao-Bo; Wang, Ting-Gui; Ho, Luis C; Yuan, Weimin; Wang, Huiyuan; Zhang, Kai; Zhang, Shaohua; Zhou, Hongyan (The Astrophysical journal, 2009)