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

Code	Display
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