@inproceedings{ijcai2003p12,
  title     = {A Tractability Result for Reasoning with Incomplete First-Order Knowledge Bases},
  author    = {Liu, Yongmei and Levesque, Hector J.},
  booktitle = {Proceedings of the Eighteenth International Joint Conference on
               Artificial Intelligence, {IJCAI-03}},
  publisher = {International Joint Conferences on Artificial Intelligence},
  editor    = {Georg Gottlob},
  pages     = {83--87},
  year      = {2003},
  url       = {https://ijcai.org/proceedings/2003/12},
}