The values for the pub-id-type attribute.
The pub-id-type attribute names the type of identifier, or the organization or system that defined the identifier, for the identifier of the journal article or a cited publication. This attribute is used on the <article-id> element, which holds an identifier for the entire article. It is also used on the <pub-id> element, which is an identifier for a publication cited in a bibliographic reference (<citation> or <nlm-citation>).
<!ENTITY % pub-id-types "coden | doi | medline | other | pii | pmid | publisher-id | sici" >