1. A. Albano, G. Ghelli and R. Orsini, ?Objects for a database programming language,? in3rd Int. Workshop Database Programming Languages, Napflion, Greece, 1991.
2. P. America and F. Van der Linden, ?A parallel object-oriented language with inheritance and sub-typing,?Proceedings of ECOOP/OOPSLA 90, October 21?25, 1990.
3. F. Banchilon, ?Object-oriented database systems,? in7th Symp. Principles of Database Systems, ACM, Austin, Texas, 1988, pp. 152?162.
4. P.A. Bernstein, V. Hadzilacos and N. Goodman,Concurrency Control and Recovery in Database Systems, Addison-Welsey: Reading, MA, 1987.
5. A. Bondavalli, N. De Francesco, D. Latella, and G. Vaglini, ?Shared abstract data types: an algebraic methodology for their specification,? inMFDBS-89, LNCS 364, Budapest, 1989, pp. 53?67.