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   51164
   So far observed distant (z>1) quasars mostly show steeper spectra in
   the 2-10 keV band than that of the cosmic X-ray background (CXB) . We
   have more than 80 well qualified AGN spectra by ASCA, but their
   properties are not well balanced due to poor observation sample of high
   z radio quiet (RQ) QSO s. A considerable fraction of low luminosity AGN
   have X-ray spectra as flat as the CXB. In this proposal we selected
   three high z RQ QSOs which were already detected in the ROSAT survey
   and/or pointing observations. We expect that these sources have
   considerable flat spectra with higher absorption. This confirmation is
   very important for AGN evolution as well as the CXB.
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