@inproceedings{ijcai2005p35,
  title     = {Propositional Abduction is Almost Always Hard},
  author    = {Nordh, Gustav and Zanuttini, Bruno},
  booktitle = {Proceedings of the Nineteenth International Joint Conference on
               Artificial Intelligence, {IJCAI-05}},
  publisher = {International Joint Conferences on Artificial Intelligence},
  pages     = {534--538},
  year      = {2005},
  url       = {https://ijcai.org/proceedings/2005/35},
}