Digital Object Identifiers (DOI) are in wide use mainly to identify information of different kind such as journal articles, research reports, data sets, official publications et cetera. However, the privately dominated DOI system is many times very cost intensive for authors. Therefore, Causation has decided not to use the DOI system.

Still, Causation supports authors to obtain additionally a DOI at ResearchGate, Zenodo,  bioRxiv.org, Figshare et cetera for their manuscript. The author himself is responsible for specifying a DOI within his article. If a DOI is missing inside a manuscript, the journal Causation will try to obtain a DOI  for the author and in the name of the author. 

Altogether, Causation has decided to use the low-cost Uniform Resource Name (URN) system of the German National Library, Frankfurt, in order to permanently address and identify online publications.

In contrast to the DOI system which is at the principal risk of bankruptcy, the state owned German National Library Frankfurt is responsible for the long-term archiving of the digital publications and has to ensure by virtue of the laws of Germany  the public, long-term availability of digital publications on the Internet.