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   PR # 21171
      We propose to observe two luminous clusters of galaxies in the red-
    shift range of 0.2-0.3 found by EMSS. These clusters show prominent  
    gravitational lensing effect and their lensed image of background    
    galaxies suggest the presence of highly concentrated lensing dark    
    matter. X-ray observations with ASCA will give us informations on the
    properties of intracluster hot gas, which is another probe of dark   
    matter distribution. X-ray  properties of gravitational lensing      
    cluster might be  a key to the study of cluster evolution and its    
    relation to dark matter.                                             
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