Consistency Checking for Qualitative Spatial Reasoning with Cardinal Directions

Skiadopoulos S, Koubarakis M.  2002.  Consistency Checking for Qualitative Spatial Reasoning with Cardinal Directions. Principles and Practice of Constraint Programming - CP 2002, 8th International Conference, CP 2002, Ithaca, NY, USA, September 9-13, 2002, Proceedings. :341–355.