SIGMAFDB: Overview of the Magdeburg-Approach to Database Federations. - Michael Höding; Kerstin Schwarz; Stefan Conrad 001; Gunter Saake; Sören Balko; A. Diekmann; Eyk Hildebrandt; Kai-Uwe Sattler; Ingo Schmitt; Can Türker (EFIS, 1999)