@Article{nebel:scivos:ki-02,
  author = 	 {B. Nebel and A. Scivos},
  title = 	 {Formal Properties of Constraint Calculi for
  Qualitative Spatial Reasoning},
  journal = 	 {K\"unstliche Intelligenz},
  year = 	 {2002},
  number =	 {4/02},
  pages =	 {14-18},
}