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   PR # 11137
    We propose the high z QSO's which were detected by the all sky survey
    of ROSAT.This proposal has selected brighter QSO's among these QSO's.
    Therefore,it is expected that the observation time of 40 ksec is
    enough to investigate the spectral structure of each QSO. The z
    dependence of spectral index is expected from a Compton reflection
    model of X-ray spectrum.  It is very important for CXB to know the
    spectral structure of QSO's with z=2-4.





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