1. Billen, R., Clementini, E.: Étude des caractéristiques projectives des objets spatiaux et de leurs relations. Revue Internationale de Géomatique 14, 145–165 (2004)
2. Lecture Notes in Computer Science;R. Billen,2004
3. Clementini, E., Di Felice, P.: Spatial Operators. ACM SIGMOD Record 29, 31–38 (2000)
4. Dugat, V., Gambarotto, P., Larvor, Y.: Qualitative Theory of Shape and Orientation. In: Proc. of the 16th Int. Joint Conference on Artificial Intelligence (IJCAI 1999), Stockolm, Sweden, pp. 45–53 (1999)
5. Gapp, K.-P.: From Vision to Language: A Cognitive Approach to the Computation of Spatial Relations in 3D Space. In: Proc. of the First European Conference on Cognitive Science in Industry, Luxembourg, pp. 339–357 (1994)