<hi xmlns="http://www.tei-c.org/ns/1.0" rend="bold">Gradman, Stefan </hi>(2009): "Interoperability. A key concept for large scale, persistent digital libraries". <hi xmlns="http://www.tei-c.org/ns/1.0" rend="italic">Digital Preservation Europe</hi> <ref xmlns="http://www.tei-c.org/ns/1.0" target="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.363.6311&rep=rep1&type=pdf">http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.363.6311&rep=rep1&type=pdf</ref> [letzter Zugriff: 25.09.2017].