This is the ValueSet that contains all the codes in Substance Classification (http://hl7.org/fhir/us/pq-cmc-fda/ValueSet/substance-classification) and Substance Classification (http://hl7.org/fhir/us/pq-cmc-fda/ValueSet/substance-classification). E.g. what you have to deal with if you get resources containing codes in either of them