Unique external identifier assigned to an article.
There may be many identifiers for a single article, and each <article-id> holds only one. While such an identifier may be a unique identifier in some system, an article can be identified in many systems. The content for this element may be assigned by a publisher, a jobber, CrossRef, or PubMed Central, for example. Examples of such identifiers include the publisher’s tracking number, a DOI, a PNAS number, etc.
The @pub-id-type attribute may be used to name the type of identifier (such as DOI or SICI), or the organization or system (such as PubMed Central) that defined this identifier. This attribute need only be used if the type is known, for example, to identify DOIs explicitly.
External Identifier: This element holds an external identifier, assigned to a document by an agency such as the publisher, an archive, an aggregator or hosting service, or CrossRef or other DOI authority. The contents of this element should not be confused with the @id attribute, which holds an internal document identifier that can be used by software to preform a simple link.
Conversion Note: An archive may attempt to carry all the identifiers associated with an article. For example, during conversion PubMed Central will create <article-id>s for identifiers that come from the publisher as elements or as attributes on the original article.
<!ELEMENT article-id (#PCDATA) >
Text, numbers, or special characters
<article dtd-version="1.1"> <front> <journal-meta>...</journal-meta> <article-meta> <article-id pub-id-type="publisher-id">1037</article-id> <article-id pub-id-type="doi">10.1128/JCM.39.7.2634-2636.2001</article-id> <article-id pub-id-type="pmid">11427581</article-id> <article-categories>...</article-categories> <title-group> <article-title>Molecular Identification of a <italic>Dietzia maris</italic> Hip Prosthesis Infection Isolate</article-title> </title-group> ...</article-meta> </front> ...</article>