%% You should probably cite rfc6809 instead of this I-D.
@techreport{ietf-sipcore-proxy-feature-00,
    number =    {draft-ietf-sipcore-proxy-feature-00},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-ietf-sipcore-proxy-feature/00/},
    author =    {Christer Holmberg and Ivo Sedlacek and Hadriel Kaplan},
    title =     {{Indication of features supported by proxy}},
    pagetotal = 12,
    year =      2012,
    month =     mar,
    day =       2,
    abstract =  {This document defines a new SIP header field, Feature-Caps, that can be used by SIP entities to indicate support of features and capabilities, in cases where the Contact header field contains a URI that does not represent the SIP entity that wants to indicate support of its features and capabilities.},
}