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   PR # 12001
     We propose to begin the systematic study of the spectra of high red-
    shift clusters of galaxies. Specifically we will make the first deter
    mination of the cluster temperature function at a redshift other than
    zero. This measurement will discriminate among various models of the
    evolution of the X-ray gas in clusters and will also constrain the
    mass density fluctuations spectrum on large scales.






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