@TechReport{	  BeckertGoreTR96,
  author	= {Bernhard Beckert and Rajeev Gor\'e},
  title		= {Free Variable Tableaux for Propositional Modal Logics},
  institution	= {Universit\"{a}t Karlsruhe, Fakult\"{a}t f\"{u}r Informatik},
  series	= {{I}nterner {B}ericht},
  number	= {41/96},
  year		= {1996}
}