@InProceedings{BeckertGore97,
  author	= {Bernhard Beckert and Rajeev Gor\'e},
  title		= {Free Variable Tableaux for Propositional Modal Logics},
  booktitle	= {International Conference on Theorem Proving with Analytic
		  Tableaux and Related Methods ({TABLEAUX} '97)},
  venue         = {Pont-{\'a}-Mousson, France},
  pages         = {91--106},
  series	= {LNCS},
  volume        = {1227},
  publisher	= {Springer},
  year		= {1997}
}