Add the text below to the HRex IG:

This implementation guide uses terminology, notations and design principles that are specific to FHIR. Before reading this implementation guide, it’s important to be familiar with some of the basic principles of FHIR as well as general guidance on how to read FHIR specifications. Readers who are unfamiliar with FHIR are encouraged to read the following prior to reading the rest of this implementation guide.

• FHIR overview
• Developer’s introduction
• (or Clinical introduction)
• FHIR data types
• Using codes
• References between resources
• How to read resource & profile definitions
• Base resource

This information should be linked to from each of the Da Vinci IGs. This is currently part of the DTR IG. http://build.fhir.org/ig/HL7/davinci-dtr/underlying_technologies.html#fhir

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