[1] [CITE@en[draft-jennings-sipping-multipart-02 - Session Initiation Protocol (SIP) Offer/Answer with Multipart Alternative]]
( ([TIME[2014-10-17 16:44:51 +09:00]] 版))
<https://tools.ietf.org/html/draft-jennings-sipping-multipart-02#section-4>