@article{MagKazHor:11:Incremental:JAR,
  title = "Tractable Extensions of the Description Logic {EL} with Numerical Datatypes.",
  author = "Despoina Magka and Yevgeny Kazakov and Ian Horrocks",
  year = "2011",
  journal = "Journal of Automated Reasoning",
  note = "To appear",
}