Zhang, Xue-Guang Cosmology, MPI for Astrophysics, Max Planck Society;
Zhang, X.-G., Dultzin, D., & Wang, T.-G. (2008). The correlation between spectral index and accretion rate for AGN. Monthly Notices of the Royal Astronomical Society, 385(2), 1087-1094. doi:10.1111/j.1365-2966.2008.12912.x.