Attribute list for the <book-id> element. The major attribute named is the @pub-type, which indicates the type of publication identifier, such as DOI or SICI.
<!ENTITY % book-id-atts "pub-id-type (%pub-id-types;) #IMPLIED" >
pub-id-type (art-access-id | coden | doaj | doi | manuscript | medline | other | pii | pmcid | pmid | publisher-id | sici) #IMPLIED
bookmeta3.ent