This is the ValueSet that contains all the codes in BR Observation Referencia (https://terminologia.saude.gov.br/fhir/ValueSet/BRObservationReferencia) and BR Observation Referencia (https://terminologia.saude.gov.br/fhir/ValueSet/BRObservationReferencia). E.g. what you have to deal with if you get resources containing codes in either of them