http://hl7.org/fhir/StructureDefinition/documentreference-sourcepatient|5.2.0

The Patient Information as known when the document was published. May be a reference to a version specific, or contained.
typedestination
baseDefinitionhttp://hl7.org/fhir/StructureDefinition/Extension
typehttp://hl7.org/fhir/StructureDefinition/Extension
Extension.value[x].typehttp://hl7.org/fhir/StructureDefinition/Reference
Extension.value[x].targetProfilehttp://hl7.org/fhir/StructureDefinition/Patient