3GPP 24.501 v20.0.0 — the document's own text
8.2.11.3 Additional information
Taught in 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
This IE is included when the Payload container type IE is set to "LTE Positioning Protocol (LPP) message container", "UPP-CMI container", "SLPP message container", or "Location services message container".