The talk will present how the use of semantic technologies can enhance the retrieval in complex document repositories. It will start with an overview of our research on the combination of semantic technologies with traditional information retrieval approaches. Based upon these concepts current research at the German National Library for Economics (ZBW) investigates the options which exist, if retrieval is not only performed on the documents themselves but on semantic representations of the documents. Finally, the talk will close with two new approaches ZBW is currently investigating: Firstly, how can semantic technologies be used to support research data management and secondly, what semantic "light-weight" options (e.g. RDFa) exist to apply semantic technologies particularly to the deep web.