@inproceedings{ijcai2009p144,
  title     = {A Semantical Account of Progression in the Presence of Defaults},
  author    = {Lakemeyer, Gerhard and Levesque, Hector J.},
  booktitle = {Proceedings of the Twenty-First International Joint Conference on
               Artificial Intelligence, {IJCAI-09}},
  publisher = {International Joint Conferences on Artificial Intelligence},
  editor    = {Hiroaki Kitano},
  pages     = {842--846},
  year      = {2009},
  url       = {https://ijcai.org/proceedings/2009/144},
}