The entries are also provided with one or more URIs from different authority files, if an entry exists there. This makes it possible to identify persons, places and institutions <hi xmlns="http://www.tei-c.org/ns/1.0" rendition="#i">across projects</hi>, both in ehd itself and when using the APIs and data publication (see also <bibl xmlns="http://www.tei-c.org/ns/1.0" corresp="https://edition-humboldt.de/W4L92XBE">Stadler 2012</bibl> on authority files in editions). For person entries, the GND is primarily used, alternatively or additionally also <ref xmlns="http://www.tei-c.org/ns/1.0" target="https://viaf.org/">VIAF</ref>. For places, on the other hand, URIs from the free geographic database <ref xmlns="http://www.tei-c.org/ns/1.0" target="https://www.geonames.org">GeoNames</ref> are used, since this achieves a high level of coverage worldwide and entries can be added by the project itself if necessary. Thus, a few localities missing in GeoNames (such as the former locations of the <ref xmlns="http://www.tei-c.org/ns/1.0" target="https://edition-humboldt.de/H0000531?l=en">Berlin Observatory</ref>) were added there.