@InProceedings{	  dixpossch90,
  author	= {J\"{u}rgen Dix and Achim Posegga and Peter. H. Schmitt},
  title		= {{M}odal {L}ogics for {A}{I} {P}lanning},
  booktitle	= {Proceedings of the First International Conference on
		  Expert Planning Systems, Brighton},
  year		= {1990},
  pages		= {157--162},
  publisher	= {Conf. Publ. No. 322},
  month		= {June}
}