Will update the observationLinkPeriod page to include mention of its use for extraction and links to the relevant sections of both the prepopulation and extraction pages Will add guidance indicating that multiple codes can be present if doing pre-population (in which case you pick the most recent of any of them). However, for extraction, there must either be only one code, or exactly one of the codes must be marked as the extraction target with an extension. (We'll define a boolean extension for that purpose.) Will also provide documentation that indicates that the extraction target must have identical scope to the Questionnaire.item. E.g. If the question is "most recent blood pressure", the selected code would have to have a semantic of "blood pressure", not "blood pressure, sitting", "blood pressure, standing", etc. I.e. the code must not assert any meaning not present in the questionnaire text. (Other codes in the list could either be exactly equivalent to the selected code or could be narrower.)