This is the CodeSystem that contains all the codes in SpecialValues (http://terminology.hl7.org/CodeSystem/special-values) and SpecialValues (http://terminology.hl7.org/CodeSystem/special-values). E.g. what you have to deal with if you get resources containing codes in either of them
Generated Narrative: CodeSystem d90c6776-070a-4707-b535-0a35f2e2298a-1583
This code system http://hl7.org/fhir/comparison/CodeSystem/d90c6776-070a-4707-b535-0a35f2e2298a-1583 defines codes, but no codes are represented here