@article{LAHS04a,
  title = "Keys, Nominals, and Concrete Domains",
  author = "Carsten Lutz and Carlos Areces and Ian Horrocks and Ulrike Sattler",
  year = "2004",
  journal = "J.\ of Artificial Intelligence Research",
  pages = "667--726",
  url = "download/2004/LAHS04a.pdf",
  volume = "23",
}