Version 0.2 pybib2web now supports the uniform resource name ([URN](https://en.wikipedia.org/wiki/Uniform_Resource_Name)) as unique identifier for resources, as alternative to the DOI. If no DOI is available for a BibTeX entry but a URN is, the URN will be used to provide a link to the entry's publisher version. Script `contrib/check-doi` has been removed to ease maintenance and distribution of pybib2web. It is only used internally at [SoSy-Lab](https://www.sosy-lab.org/).