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   61228
   We propose a systematic follow-up observation of the ASCA Large Sky
   Survey. The LSS is the first unbiased sky survey above 2 keV (up to 10
   keV) with an imaging instrument and covers a continuous field of 6 deg2
   with exposure tume of 30 ks. The average spectrum of detected sources
   is harder than that of nearby type I AGN, suggesting that the spectral
   paradox is beginining to be solved. However, it is still unclear what
   are these hard sources. In order to study the nature of the 2-10 keV
   source polulation and thus provide a clear picture of the composition
   of the CXB, precise mesurement of the individual source spectrum is a
   crucial task. The main aim is to to discriminate whether they are
   higyly absorbed sources (type II AGN) or other type of sources.
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