text: When citing this digital document, please use the following Uniform Resource Name (URN)
  To refer to this document on the net, please use the following Persistent Uniform Resource Locator (PURL):
  You can also test the resolution of the link here: urn:nbn:de:bo133-1-335437
  Using a Persistent Identifier (hier: URN) allows electronic documents to be referenced in a stable, globally unambiguous and non-location-dependent manner. It guarantees reliability in citing sources even if the Uniform Resource Locator (URL) changes. This is why URNs are suitable for permanently guaranteed citation in scientific papers.
  URNs cannot be called up directly in a browser but are translated into URLs by a resolving service. The persistent resolution of these links is carried out by the URN-Resolver der Deutschen Nationalbibliothek.