This is the ValueSet that contains all the codes in x_ParticipationEntVrf (http://terminology.hl7.org/ValueSet/v3-xParticipationEntVrf) and x_ParticipationEntVrf (http://terminology.hl7.org/ValueSet/v3-xParticipationEntVrf). E.g. what you have to deal with if you get resources containing codes in either of them