Xu, D. W. High Energy Astrophysics, MPI for Extraterrestrial Physics, Max Planck Society;
Komossa, Stefanie High Energy Astrophysics, MPI for Extraterrestrial Physics, Max Planck Society;
Xu, D. W., Komossa, S., Wei, J. Y., & Zheng, X. Z. (2003). An active galactic nucleus sample with high X-ray-to-optical flux ratio from RASS. II. Optical emission line properties of Seyfert 1-type active galactic nuclei. The Astrophysical Journal, 590, 73-85.
