%% You should probably cite draft-ietf-avtcore-clksrc instead of this I-D.
@techreport{williams-avtcore-clksrc-01,
    number =    {draft-williams-avtcore-clksrc-01},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-williams-avtcore-clksrc/01/},
    author =    {Aidan Williams and Kevin Gross and Ray van Brandenburg and Hans Stokking},
    title =     {{RTP Clock Source Signalling}},
    pagetotal = 21,
    year =      2012,
    month =     jun,
    day =       5,
    abstract =  {NTP timestamps are used by several RTP protocols for synchronisation and statistical measurement. This memo specificies SDP signalling identifying NTP timestamp clock sources and SDP signalling identifying the media clock sources in a multimedia session.},
}