• Dan Suciu, Jan Paredaens,
  The complexity of the evaluation of complex algebra expressions
  Published in Journal of Computer and System Sciences, vol. 55 , no. 2 , pp. 322-343 , October , 1997
  
• Dan Suciu, Jan Paredaens,
  Any Algorithm in the Complex Object Algebra needs Exponential Space to Compute Transitive Closure
  In Proceedings of 13th ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems, pp. 201-209, May, 1994
  Note: The postscript formatting differs slightly from that in the proceedings