Salem Benferhat Safa Yahi Complexity and Cautiousness Results for Reasoning from Partially Preordered Belief Bases. 817-828 2009 ECSQARU http://dx.doi.org/10.1007/978-3-642-02906-6_70 conf/ecsqaru/2009 db/conf/ecsqaru/ecsqaru2009.html#BenferhatY09