@INPROCEEDINGS{amast93,
      AUTHOR={N. Halbwachs and F. Lagnier and P. Raymond},
      TITLE={Synchronous observers and the verification of reactive systems},
      BOOKTITLE={Third Int. Conf. on Algebraic Methodology and
              Software Technology, AMAST'93},
      ADDRESS={Twente},
      MONTH={June },
      EDITOR={M. Nivat and C. Rattray and T. Rus and G. Scollo},
      PUBLISHER={Workshops in Computing, Springer Verlag},
      YEAR=1993
   }