ext-link-type Type of External Link

Type of external link; may include a specific source (for example, “pdb”, “pir”), identifier type (for example, “doi”), or access method (for example, “ftp”, “uri”).
OPTIONAL on elements: <ext-link>, <related-article>
Value Meaning
Text, numbers, or special characters Names the type of link (for example, “doi” or “uri”) or the type of access (“ftp”).
Restriction This is an optional attribute; there is no default.
Tagged Sample

Identifying a link as a URI

...
<list-item>
 <label>7.</label>
 <p>Comments, suggestions, or questions on this document 
  should be addressed to the Defense Standardization Program 
  Office (<abbrev>DSPO</abbrev>), 8725 John J. Kingman Road, 
  Stop 5100, Fort Belvoir, VA 22060-6220 or emailed to 
  <email>DSPO@dla.mil</email>. Since contact information 
  can change, you may want to verify the currency of this 
  address information using the ASSIST Online database at 
  <ext-link ext-link-type="uri" xlink:href="https://assist.dla.mil"
   >https://assist.dla.mil</ext-link>.</p>
</list-item>
...