• Christos Papadimitriou, Dan Suciu, Victor Vianu,
  Topological queries in spatial databases
  Published in Journal of Computer and Systems Sciences, vol. 58 , no. 1 , pp. 29-53 , 1999
  
• Christos Papadimitriou, Dan Suciu, Victor Vianu,
  Topological queries in spatial databases
  In Proceedings of 15th ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems, June, 1995