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We present in this paper the progress report of the building of two cryogenic sapphire oscillators (CSO) at LPMO. A description of our original resonator configuration is discussed. The measurement of a short-term frequency instability better than 2 · 10−14 for short integration times is presented. We also demonstrated an exceptional long term frequency stability of better than 5 · 10−14 over one day. We finally report the usefullness of CSO in the characterization of state of the art ultra stable quartz cristal oscillators in a simple way of measurement.