This is the CodeSystem that contains all the codes in PCT GFE Frequency Code System (http://hl7.org/fhir/us/davinci-pct/CodeSystem/PCTGFEFrequency) and PCT GFE Frequency Code System (http://hl7.org/fhir/us/davinci-pct/CodeSystem/PCTGFEFrequency). E.g. what you have to deal with if you get resources containing codes in either of them