In elements <graphic>, <inline-graphic>, and <media>, this attribute must be used if the element is used.
| Value |
Meaning |
| Text, numbers, or special characters |
A pointer (a URL) to a resource. |
In elements <abbrev>, <award-group>, <bio>, <chem-struct>, <collab>, <conference>, <contrib>, <element-citation>, <email>, <ext-link>, <funding-source>, <inline-supplementary-material>, <institution>, <issue-id>, <license>, <long-desc>, <mixed-citation>, <named-content>, <nlm-citation>, <product>, <pub-id>, <related-article>, <related-object>, <self-uri>, <supplementary-material>, <uri>, and <volume-id>, this attribute may be used if the element is used.
| Value |
Meaning |
| Text, numbers, or special characters |
A pointer (a URL) to a resource. |