Property:External formatter URI
From Wijchen Samenwerkingswijzer
"External formatter URI" is a predefined property provided by Semantic MediaWiki to specify an external resource with a placeholder. The URI is expected to contain a placeholder that will be adjusted with an external identifier value to form a valid resource reference. This property is pre-deployed (also known as special property) and comes with additional administrative privileges but can be used just like any other user-defined property.
