[1] RFC 7669 - Assigning Digital Object Identifiers to RFCs (2015-10-24 08:18:30 +09:00 版) https://tools.ietf.org/html/rfc7669

[2]

New Crossref DOI display guidelines are on the way – Crossref Blog (2016-10-05 21:30:20 +09:00) http://blog.crossref.org/2016/09/new-crossref-doi-display-guidelines.html

The updated Crossref DOI Display guidelines recommend that https://doi.org/ be used and not http://dx.doi.org/ in DOI links. Originally the “dx” separated the DOI resolver from the International DOI Foundation (IDF) website but this has changed and the IDF has already updated its recommendations so we are bringing ours in line with theirs.