@InProceedings{scivos:nebel:cosit-01,
  author = 	 {Alexander Scivos and Bernhard Nebel},
  title = 	 {Double-Crossing: Decidability and Computational 
                  Complexity of a Qualitative Calculus for Navigation},
  booktitle = 	 {Spatial Information Theory: Foundations of Geographic Information Science (COSIT-2001)},
  year =	 2001,
  publisher =	 spring,
  address = "Morro Bay, CA"
}