Agree with submitter's suggestions (as pre-applied).  Further additions to the text are still needed for clarification.  Move that in addition to the pre-applied changes the text below be included in the Using MED-RT on FHIR page: The MED-RT Code System includes relationships between MED-RT concepts and concepts in external Code Systems, as well as relationships between concepts only in the external Code Systems. The external Code Systems that MED-RT references include RxNorm, MeSH, and SNOMED CT US Edition. The representation of the contents of MED-RT in a FHIR CodeSystem resource may contain all concepts defined as existing solely in MED-RT, and relationships between concepts defined within MED-RT, and between MED-RT concepts and a concept in an external code system. In addition, ConceptMap resource(s) are needed to represent the relationships in MED-RT that exist between external code systems. For more information on MED-RT, Currently all references to external code systems in MED-RT are to a specific version of the external code system. See  https://ncit.nci.nih.gov/ncitbrowser/pages/vocabulary.jsf?dictionary=MED-RT .