In addition to the many reasons noted in the comments for this tracker to keep Citation Resource in FHIR, there are other Resources that now reference Citation directly including ResearchStudy and SubstanceDefinition by the BRR WG and DiagnosticReport by the OO WG.  This is further evidence that Citation is specifically needed for healthcare integration (especially to integrate literature references and scientific knowledge with healthcare). Also, the EBMonFHIR project and functionally expanded to the COVID-19 Knowledge Accelerator with more than a dozen active working groups includes the "domain knowledge that makes HL7 the best ones to do it" specifically for the domain of healthcare. We will add documentation on the rationale for the Citation resource: Although citations as a concept are certainly not unique to healthcare, their use within healthcare contexts is ubiquitous, especially as part of the need to cite literature references and scientific knowledge as part of supporting evidence. This need is already manifest in references to the Citation resource from other FHIR resources including ResearchStudy, SubstanceDefinition, and DiagnosticReport. In addition, citations of evidence are a critical aspect of evidence-based medicine and structures to represent citation information are a necessary modeling component in the EBM-on-FHIR project. Without a resource dedicated to this concept, evidence-based medicine concepts and approaches would need to rely on extensions and/or non-FHIR-based solutions to exchange citation information, resulting in more complex and difficult to implement and maintain resource types to support evidence-based medicine. === In addition, add to the Boundaries and Relationships section a discussion of the alternative external approaches (e.g. RefML, MedLine) and an explanation of why the use of Citation allows for better integration with FHIR use cases.