Every publication on OPUShtw automatically receives a citable URN (Uniform Resource Name). Unlike a URL, for example, this persistent identifier (PI) provides a unique and permanent reference to the resource in question, regardless of where it is stored. This enables the long-term availability of online resources. The German National Library manages and assigns the URN from the namespace "urn:nbn:de".

In addition, it is possible to assign a DOI to the published document if it has not already been assigned. The use of URNs and DOIs fulfils the international guidelines for scientific citations.