@inproceedings{ijcai2009p146,
  title     = {Combining RCC-8 with Qualitative Direction Calculi: Algorithms and Complexity},
  author    = {Liu, Weiming and Li, Sanjiang and Renz, Jochen},
  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     = {854--858},
  year      = {2009},
  url       = {https://ijcai.org/proceedings/2009/146},
}