van der Torre, Leendert W. N. Max Planck Society;
van der Torre, L. W. N., & Tan, Y.-H. (1999). An Update Semantics for Defeasible Obligations. In K. B. Laskey, & H. Prade (Eds.), Proceedings of the 15th Conference on Uncertainty in Artificial Intelligence (UAI-99) (pp. 631-638). San Francisco, USA: Morgan Kaufmann.