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   71193
   The origin of the Cosmic X-ray background (CXB) has been one of the key
   issues of X-ray astronomy. We propose follow up observations of 8
   selected hard X-ray sources discovered by the serendipitous source
   survey project with ASCA. AXAF observations of these sources to
   determine positions were already approved. These sources have 2-10 keV
   fluxes below 5 x 10**(-13) erg/cm2/s. ASCA 0.7-2/2-10 keV counting
   rates that require them to either have power law photon indecies
   flatter than 1.0, or if they have intrinsic slopes of 1.7, have column
   density greater than Nh = 2 x 10**22/cm2.
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