This code system http://terminology.hl7.org/CodeSystem/primary-source-type defines the following codes:

CodeDisplay
lic-board License Board
prim Primary Education
cont-ed Continuing Education
post-serv Postal Service
rel-own Relationship owner
reg-auth Registration Authority
legal Legal source
issuer Issuing source
auth-source Authoritative source
 <status value="draft"/> <experimental value="false"/> <date value="2018-06-05T14:06:02+00:00"/> <publisher value="HL7 (FHIR Project)"/> <contact> <telecom> <system value="url"/> <value value="http://hl7.org/fhir"/> </telecom> <telecom> <system value="email"/> <value value="fhir@lists.hl7.org"/> </telecom> </contact> <contact> <telecom> <system value="url"/> <value value="http://hl7.org/fhir"/> </telecom> <telecom> <system value="email"/> <value value="fhir@lists.hl7.org"/> </telecom> </contact> <description value="Type of the validation primary source"/> <caseSensitive value="true"/> <valueSet value="http://terminology.hl7.org/ValueSet/verificationresult-primary-source-type"/> <content value="complete"/> <concept> <code value="lic-board"/> <display value="License Board"/> </concept> <concept> <code value="prim"/> <display value="Primary Education"/> </concept> <concept> <code value="cont-ed"/> <display value="Continuing Education"/> </concept> <concept> <code value="post-serv"/> <display value="Postal Service"/> </concept> <concept> <code value="rel-own"/> <display value="Relationship owner"/> </concept> <concept> <code value="reg-auth"/> <display value="Registration Authority"/> </concept> <concept> <code value="legal"/> <display value="Legal source"/> </concept> <concept> <code value="issuer"/> <display value="Issuing source"/> </concept> <concept> <code value="auth-source"/> <display value="Authoritative source"/> </concept> </CodeSystem>