http://hl7.org/fhir/StructureDefinition/artifact-reference|5.2.0

A reference to a resource, canonical resource, or non-FHIR resource.

element_id	types
Extension
Extension.url	uri
Extension.value[x]	Reference,canonical,uri
Extension
Extension.id	http://hl7.org/fhirpath/System.String
Extension.extension	Extension
Extension.url	uri
Extension.value[x]	Reference,canonical,uri