@INPROCEEDINGS{Dondrup2014,
  author = {C. Dondrup and N. Bellotto and M. Hanheide},
  title = {A Probabilistic Model of Human-Robot Spatial Interaction Using a
  Qualitative Trajectory Calculus},
  booktitle = {AAAI Spring Symposium -- Qualitative Representations for Robots},
  year = {2014},
  pages = {18-25}
}