1. Batini, C., Ceri, S., Navathe, S.B.: Conceptual Database design: an Entity- Relationship Approach. Benjamin/Cummings Publishing Company (1992)
2. Bergamaschi, S., Sartori, C.: Chrono: a conceptual design framework for temporal entities. Technical Report CSITE-011-98, CSITE - CNR (1998),
ftp://wwwdb.deis.unibo.it/pub/reports/CSITE-011-98.pdf
3. Chen, P.: The Entity-Relationship model - towards a unified view of data. ACM Trans. on Database Systems 1(1), 9–36 (1976)
4. Elmasri, R., El-Assal, I., Kouramajian, V.: Semantics of temporal data in an extended ER model. In: 9th Int. Conf. on the Entity–Relationship Approach, Lausanne, Switzerland, pp. 239–254 (1990)
5. Lecture Notes in Computer Science;R. Elmasri,1993