  We present the results and parameterization of the 0.5-2 keV Luminosity
Function of AGNs from various ROSAT Surveys, ranging from the ROSAT bright
Survey from the ROSAT All-Sky Survey (RASS) to the Ultra-Deep survey on the
Lockman hole. A Luminosity-dependent density evolution model, where the density
evolution rate drops at low luminosities, gives an excellent parametric
description of the overall XLF covering wide ranges of redshift and luminosity.
  The number density evolution of high-luminosity AGNs in our sample shows a
similar behavior to optical and radio surveys, except that we do not find
evidence for the rapid decrease of the number density at z>2.7. The discrepancy
is marginally significant and including more deep survey results would make
better determination of the behavior.
