1. Abiteboul, S., Hull, R., Vianu, V.: Foundations of Databases. Addison- Wesley, Reading (1995)
2. LNAI;J.-F. Baget,1999
3. LNAI;C. Bos,1997
4. Baget, J.-F., Genest, D., Mugnier, M.-L.: Knowledge acquisition with a pure graph-based knoweldge representation model — application to the sisyphus-i case study. In: Proc. KAW 1999 (1999)
5. LNAI;F. Baader,1999