%% You should probably cite rfc4485 instead of this I-D.
@techreport{ietf-sip-guidelines-09,
    number =    {draft-ietf-sip-guidelines-09},
    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-sip-guidelines/09/},
    author =    {Henning Schulzrinne and Jonathan Rosenberg},
    title =     {{Guidelines for Authors of Extensions to the Session Initiation Protocol (SIP)}},
    pagetotal = 23,
    year =      2005,
    month =     feb,
    day =       16,
    abstract =  {The Session Initiation Protocol (SIP) is a flexible yet simple tool for establishing interactive communications sessions across the Internet. Part of this flexibility is the ease with which it can be extended. In order to facilitate effective and interoperable extensions to SIP, some guidelines need to be followed when developing SIP extensions. This document outlines a set of such guidelines for authors of SIP extensions. This memo provides information for the Internet community.},
}