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    PR # 31255                                                                   
     We propose to observe two luminous clusters of galaxies in the redshi       
     ft range of 0.2 0.3 found by EMSS. These clusters show prominent grav       
     itational lensing effect and their lensed image of background galaxie       
     s suggest the presence of highly concentrated lensing dark matter. X-       
     ray observations with ASCA will give us informations on the propertie       
     s of intracluster hot gas, which is another probe of dark matter dist       
     ribution. X-ray properties of gravitational lensing cluster might be        
     a key to the study of  cluster evolution and its relation to dark mat       
     ter.                                                                        
                                                                                 
                                                                                 
                                                                                 
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