1. S. Abiteboul and C. Beeri. On the Power of Languages for the Manipulation of Complex Objects. Rapports de Recherche 846, INRIA, Domaine de Voluceau Rocquencourt 78153 Le Chesnay Cedex-France, May 1988.
2. Malcolm Atkinson, Francois Bançilhon, David De Witt, Klaus Dittrich, David Maier, and Stanley Zdonik. The Object-Oriented Database System Manifesto. In Deductive and Object-oriented Databases. Elsevier Science Publishers, Amsterdam, Netherlands, 1990.
3. R.M. Amadio and L. Cardelli. Subtyping Recursive Types. Digital Systems Research Center Reports 62, DEC SRC Palo Alto, August 1990.
4. M.P. Atkinson, K.J. Chisholm, and W.P. Cockshott. PS-Algol: An Algol with a Persistent Heap. ACM SIGPLAN Notices, 17(7), July 1981.
5. S. Abiteboul, P.C. Fischer, and H.J. Schek. Nested Relations and Complex Objects in Databases, volume 361 of Lecture Notes in Computer Science. Springer-Verlag, 1989.