1. S. Abiteboul, R. Hull, and V. Vianu. Foundations of Databases. Addison-Wesley, 1995.
2. E. Bertino, E. Ferrari and G. Guerrini. A Formal Temporal Object-Oriented Data Model. Technical Report 141-95, University of Milano, 1995.
3. T. Cheng and S. Gadia. An Object-Oriented Model for Temporal Databases. In Proc. of the Int'l Work. on an Infrastructure for Temporal Databases, 1993.
4. J. Clifford and A. Crocker. The Historical Relational Data Model (HRDM) Revisited. In A. Tansel et al., editors, Temporal Databases: Theory, Design, and Implementation, pp. 6–26. Benjamin/Cummings, 1993.
5. J. Clifford and A. Croker. Objects in Time. In Proc. 4th IEEE Int'l Conf. on Data Engineering, pp. 11–18, 1988.