3GPP 24.501 v20.0.0 — the document's own text
8.2.1.5 EAP message
Taught in 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
EAP message IE is included if the AUTHENTICATION REQUEST message is used in an EAP based primary authentication and key agreement procedure.