Laura Giordano Valentina Gliozzi Nicola Olivetti Camilla Schwind Tableau calculus for preference-based conditional logics: PCL and its extensions. 2009 10 ACM Trans. Comput. Log. 3 http://doi.acm.org/10.1145/1507244.1507251 db/journals/tocl/tocl10.html#GiordanoGOS09