%% You should probably cite draft-ietf-sipping-gruu-reg-event instead of this I-D.
@techreport{kyzivat-sipping-gruu-reg-event-03,
    number =    {draft-kyzivat-sipping-gruu-reg-event-03},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-kyzivat-sipping-gruu-reg-event/03/},
    author =    {Paul Kyzivat},
    title =     {{Reg Event Package Extension for GRUUs}},
    pagetotal = 11,
    year =      2005,
    month =     jul,
    day =       15,
    abstract =  {This draft defines an extension to RFC 3680 {[}1{]} for representing the GRUU associated with a Contact.},
}