@incollection{Conr98d,
author = {S.~Conrad},
booktitle = {{Datenbank-Management}},
editor = {C.~Rautenstrauch},
publisher = {Interest-Verlag},
series = {Sammelwerk, 20. Aktualisierung},
title = {{F{\"o}deration heterogener Datenbanken}},
year = {1998}
}