Why is it that sometimes in bibliography, DOI information is added?

Question

When I'm casually browsing through bibliography section of preprints, sometimes I find that an author will also include the DOI information in the citation.

For example, I just picked a random Arxiv paper from today: https://arxiv.org/pdf/2207.06887.pdf

Observe that in the citation section, some references have a DOI attached to it, but others do not.

I've observed this in many preprints and publications.

1. Is there a good reason to add the DOI information?
2. Why is it that sometimes certain references have DOI information, but others do not? Is this a citation consistency issue?

Thanks!

Answer 1

1. Yes, because it makes it easier to find the referenced document, but not all documents have an associated DOI.
2. In an arXiv submission, there's no guarantee of consistency, because this is up to the authors. For instance, the authors may have compiled the list of references from references downloaded from publishers' websites, which typically contain the DOIs, and manually inserted references from different authors, which might not be consistent. Instead, when publishing in a journal, the copy editor typically tries to ensure consistency according to the publisher's guidelines (well, the world is not ideal and not all do, but some certainly work reasonably well), either by adding the missing DOIs or other information themselves or asking the authors to make the additions.
3. A lot of software packages used to help researchers manage their resources (take genei.io) can use the DOIs to look up related papers and build relationship graphs that help when performing a literature search. This is beyond the obviously useful property of simply being able to generate a clickable link for you.

Answer 2

it's good practice to include DOI links if the author/publisher can find them. Lots of stuff doesn't have a DOI but where one is available it's important that it persistently links to the content that the authors intended.

Disclosure: I work for Crossref (a nonprofit registration agency of the DOI Foundation) and we have about 130 million DOI records.

Publishers and others (about 17k of them as of today) join Crossref and commit to keeping the metadata up to date and ensure those links keep resolving in perpetuity.

Hope this helps!

Answer 3

Frankly, it's probably just a matter of some output formatting of reference manager software. If the doi is in the database, it gets included, otherwise it gets left blank. On journal publication, page editors might demand better.