In elements <milestone-end> and <milestone-start>, this attribute may be used if the element is used.
| Value |
Meaning |
| An identifier (IDREF) |
Points to the existing identifier |
In elements <overline-end> and <underline-end>, this attribute must be used if the element is used.
| Value |
Meaning |
| An identifier (IDREF) |
Points to the existing identifier |
In elements <aff>, <author-notes>, <award-group>, <award-id>, <bio>, <contrib>, <def>, <funding-source>, <funding-statement>, <sig>, <sig-block>, <term>, and <xref>, this attribute may be used if the element is used.
| Value |
Meaning |
| One or more identifiers (IDREFS) |
Points to one or more existing identifiers |