@misc{rfc6993,
    series =    {Request for Comments},
    number =    6993,
    howpublished =  {RFC 6993},
    publisher = {RFC Editor},
    doi =       {10.17487/RFC6993},
    url =       {https://www.rfc-editor.org/info/rfc6993},
    author =    {Peter Saint-Andre},
    title =     {{Instant Messaging and Presence Purpose for the Call-Info Header Field in the Session Initiation Protocol (SIP)}},
    pagetotal = 5,
    year =      2013,
    month =     jul,
    abstract =  {This document defines and registers a value of "impp" ("instant messaging and presence protocol") for the "purpose" header field parameter of the Call-Info header field in the Session Initiation Protocol (SIP).},
}