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”, “aoi”), or access method (for example, “ftp”, “uri”).
OPTIONAL on elements: <ext-link>, <related-article>, <related-object>
Value Meaning
Text, numbers, or special characters The type of link, for example, “doi”, “aoi” or “ftp”.
Restriction @ext-link-type is an optional attribute; there is no default.

Suggested usage

If the external source is not in the list below, the type of link or type of access should be named.
aoi
Astronomical Object Identifier
doi
Digital Object Identifier
ec
Enzyme nomenclature/
email
Email address
ftp
File Transfer Protocol
gen
GenBank identifier
genpept
Translated protein-encoding sequence database
highwire
HighWire Press intrajournal
nlm-ta
NLM title abbreviation
pdb
Protein Data Bank
pgr
Electronic Plant Gene Register
pir
Protein Information Resource
pirdb
Protein information resource
pmcid
PubMed Central identifier
pmid
PubMed identifier
sprot
Swiss-Prot; now part of UniProt/
uri
Website or web service
Tagged Sample

Identifying a link as a URL

...
<ext-link xlink:href="http://www.ncemch.org/pubs/PDFs/breastfeedingTIB.pdf" 
  ext-link-type="url">http://www.ncemch.org/pubs/PDFs/breastfeedingTIB.pdf</ext-link>
...