[sevenseventen]

or vice versa! Although DOI RA's are organized functionally rather than regionally. CrossRef -- for journal articles -- is by far the largest RA.

DOI's are far, far more centralized in that CrossRef issues many orders of magnitude more DOI's than all of the others.

The cite-and-be-cited-by use case for scholarly articles is way more compelling than any other use case devised for DOI's.