@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}
}