@INPROCEEDINGS{BHS93,
AUTHOR = {Bernhard Beckert and Reiner H\"{a}hnle and
Peter H. Schmitt},
TITLE = {The Even More Liberalized $\delta$-Rule in Free Variable
Semantic Tableaux},
BOOKTITLE = {3rd Kurt G\"{o}del Colloquium ({KGC})},
PLACE = {Brno, Czech Republic},
EDITOR = {G. Gottlob and A. Leitsch and D. Mundici},
PUBLISHER = {Springer},
SERIES = {LNCS},
VOLUME = {713},
PAGES = {108--119},
MONTH = aug,
YEAR = {1993}
}