The SIP P-Served-User Private-Header (P-Header) for the 3GPP IP Multimedia (IM) Core Network (CN) Subsystem. - Hans Erik van Elburg (RFC, 2009)

An Extension to the Session Initiation Protocol (SIP) for Request History Information. - Mary Barnes; François Audet; Shida Schubert; Hans Erik van Elburg; Christer Holmberg (RFC, 2014)

Session Initiation Protocol (SIP) History-Info Header Call Flow Examples. - Mary Barnes; François Audet; Shida Schubert; Hans Erik van Elburg; Christer Holmberg (RFC, 2014)

The Session Initiation Protocol (SIP) P-Private-Network-Indication Private Header (P-Header). - Hans Erik van Elburg; Keith Drage; Mayumi Ohsugi; Shida Schubert; Kenjiro Arai (RFC, 2014)