Let’s say you’ve capitulated to all our nudging and have just begun supplying references along with your DOIs’ metadata records. The submission logs that come back confirming your successful metadata deposits now have a bunch of extra ‘stuff’ in them.
Instead of just a <msg>Successfully added</msg> or <msg>Successfully updated</msg> message for each submitted DOI (or, hopefully rarely, an error message), now you see a separate diagnostic for each submitted reference your publications’ reference lists.
These will return one of three status results:
- status=“error”
- status=“resolved_reference”
- status=“stored_query”
Let’s look at each in context. In the example submission log in our documentation, the very first reference submitted returned an error
<citation key="10.5555/example_bb0030" status="error">Either ISSN or Journal title or Proceedings title must be supplied.</citation>
What kind of reference would result in that error? Well, it would have to be a reference where each element is tagged individually (aka, “a structured citation”) because that’s the only situation which requires an ISSN or Journal/Proceedings title. For example:
<citation key="ref1">
<author>Dobbs</author>
<volume>13</volume>
<issue>2</issue>
<first_page>16</first_page>
<cYear>2023</cYear>
<article_title>Cat Herding: A Systematic Review</article_title>
</citation>
The error itself is pretty straightforward in this case. When your publication is citing a journal article or conference paper, the structured reference data has to include some way to identify the journal or conference proceedings that it’s a part of. So, adding the journal title or title abbreviation like this would take care of the problem.
<citation key="ref1">
<journal_title>Journal of Impossible Tasks</journal_title>
<author>Dobbs</author>
<volume>13</volume>
<issue>2</issue>
<first_page>16</first_page>
<cYear>2023</cYear>
<article_title>Cat Herding: A Systematic Review</article_title>
</citation>
The second reference diagnostic in that log returns the status stored_query like this
<citation key="10.5555/example_bb0005" status="stored_query"></citation>
While further down the list, you can see a resolved_reference status like this
<citation key="10.5555/example_bb0015" status="resolved_reference">10.1590/S0006-87051960000100077</citation>
Both of those were the result of references that were formatted in a completely valid way. We know this, because the status was not “error”. So, what’s the difference between them?
In simplest terms, resolved_reference means our reference matching system could successfully match the reference that was supplied in that metadata deposit to the metadata associated with a specific DOI. That is, your publication is citing something, and we’ve figured out what exactly it was citing.
In contrast, stored_query means that we couldn’t find a distinct match. We don’t know what exactly your publication was citing via that reference. When that happens, the reference is “stored” for later re-querying. Periodically, we’ll try to match it again, in case the cited publication has been registered in the meanwhile.
When a citation match has been found, the DOI of the cited item is displayed in the submission log diagnostic. In our example, that’s 10.1590/S0006-87051960000100077
The reference that produced this citation match may have looked like this
<citation key="10.5555/example_bb0015">
<doi>10.1590/S0006-87051960000100077</doi>
</citation>
Or like this
<citation key="10.5555/example_bb0015">
<journal_title>Bragantia</journal_title>
<author>Bacchi</author>
<volume>19</volume>
<first_page>XLI</first_page>
<cYear>1960</cYear>
</citation>
Or like this
<citation key="10.5555/example_bb0015">
<unstructured_citation>Bacchi, O. (1960). Estudos sôbre a conservação de sementes. V - alface. Bragantia, 19(unico), XLI–XLV.</unstructured_citation>
</citation>
Any of those, as well as many variations of the later two could produce a successful citation match to 10.1590/S0006-87051960000100077 based on the metadata supplied to Crossref by its publisher.
A stored_query result, where a citation match has not been found, typically means that the referenced publication has not been registered with Crossref. While the majority of DOIs for scholarly publications are registered with Crossref, not all scholarly publications have DOIs (this is especially true for content that was published prior to the advent of the DOI system) and not all DOIs are Crossref DOIs. If a reference is citing something that isn’t registered with Crossref, then we won’t be able to match your reference to an identifier.
In some cases, the lack of a citation match is due to an inaccuracy in the way the citation has been submitted or formatted.
One common example tends to happen when an author is citing a paper directly from a prepublication manuscript, and therefore puts the first page number “1” in their reference and the publisher passes this false, placeholder page number along in the reference they submit to Crossref. Ultimately, once that cited paper goes on to be published as an article in a journal, it’s given some other page range that doesn’t begin with “1”. So, the page number reference doesn’t end up matching the page number in the cited work’s metadata record, and no citation match can be made.
For example, if an item that you’re registering cites the article “Damage Tolerance Related to the Damage Area of Impacted Carbon/Epoxy Composite Laminates” in volume 57 issue 19 of Journal of Composite Materials, but you supply the reference like this:
<citation key="5555.1">
<unstructured_citation>Targino, T. G., et al. (2023). Damage tolerance related to the damage area of impacted carbon/epoxy composite laminates. Journal of Composite Materials, 57(19), 1-9</unstructured_citation>
</citation>
That won’t be effective in producing a citation match to its DOI 10.1177/00219983231181942 because the page range in the metadata for that DOI is 2985-2993, not 1-9. However, if the first page number, or page range, was entirely omitted from the reference, that would match successfully. Page numbers can help disambiguate one item from another, but they’re not required - an inaccurate page number hurts more than an accurate one helps.
In other instances, a missing citation match may be due to an overall sparsity of information in the reference. This is especially a problem with structured references where each element has its own tags. Unstructured references, where a whole formatted citation is submitted as one block of text, tend to be a bit more flexible.
So, to take another example, if an item that you’re registering cites the article “ Cosmological consequences of Brans–Dicke theory in 4D from 5D scalar-vacuum” in volume 139, issue 2 of The European Physical Journal Plus, but you submit a reference like this:
<citation key="5555.2">
<journal_title>Eur Phys J Plus</journal_title>
<author>Lambiase</author>
<cYear>2024</cYear>
</citation>
That’s unlikely to produce a successful match to that cited work’s DOI - 10.1140/epjp/s13360-024-04905-w - simply because there’s not enough data included. The publication year, journal abbreviation, and first author’s surname are accurate, but including the volume and issue numbers and/or the article title would be more effective.
And, of course, the simplest and most foolproof method to submit a reference is always to just use the DOI, if it exists, e.g.
<citation key="5555.3">
<doi>10.5555/12345678</doi>
</citation>
As long as that DOI exists in Crossref’s system that is a 100% guarantee that you’ll end up with a successful citation relationship between your publication and the item it cites.