@misc{rfc4964,
    series =    {Request for Comments},
    number =    4964,
    howpublished =  {RFC 4964},
    publisher = {RFC Editor},
    doi =       {10.17487/RFC4964},
    url =       {https://www.rfc-editor.org/info/rfc4964},
    author =    {Jan Holm and Andrew Allen and Thomas Hallin},
    title =     {{The P-Answer-State Header Extension to the Session Initiation Protocol for the Open Mobile Alliance Push to Talk over Cellular}},
    pagetotal = 32,
    year =      2007,
    month =     sep,
    abstract =  {This document describes a private Session Initiation Protocol (SIP) header (P-header) used by the Open Mobile Alliance (OMA) for Push to talk over Cellular (PoC) along with its applicability, which is limited to the OMA PoC application. The P-Answer-State header is used for indicating the answering mode of the handset, which is particular to the PoC application. This memo provides information for the Internet community.},
}