@INPROCEEDINGS{Straccia97, AUTHOR ="Straccia, Umberto", TITLE ="A Sequent Calculus for Reasoning in Four-Valued Description Logics", BOOKTITLE =TABLEAUX-97, series = LNAI, number = 1227, ADDRESS ="Pont-{\`{a}}-Mousson, France", YEAR ="1997", pages = "343--357" }