(extra article near the end)

For canonical references, see below. The general references are handled by the Reference type. which contains at least one of a reference (literal reference), an identifier(logical reference), and a display (text description of target). In addition, it may * a * contain a target type

Also, further below in the same page (http://hl7.org/fhir/2018May/bundle.html#references)

(e.g. OIDs * it UUIDSs or UUIDs *)