A DOI is a bit different than a standard identifier such as a ISBN in that there are multiple 'registries'[0], and they need to be paid for (it is as good as i

A DOI is a bit different than a standard identifier such as a ISBN in that there are multiple 'registries'[0], and they need to be paid for (it is as good as it gets for persistence aspirations these days) [0]https://www.doi.org/RA_Coverage.html https://www.doi.org/RA_Coverage.html