• Marc Gyssens, Dan Suciu, Dirk Van Gucht,
  Equivalence and Normal Forms for the Restricted and Bounded Fixpoint in the Nested Algebra
  Published in Information and Computation, vol. 164 , no. 1 , pp. 85-117 , 2001
  
• Marc Gyssens, Dan Suciu, Dirk Van Gucht,
  The restricted and the bounded fixpoint closures of the nested relational algebra are equivalent
  In Proceedings of the Workshop on Database Programming Languages, September, 1995