%% You should probably cite rfc8197 instead of this I-D.
@techreport{ietf-sipcore-status-unwanted-00,
    number =    {draft-ietf-sipcore-status-unwanted-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-status-unwanted/00/},
    author =    {Henning Schulzrinne},
    title =     {{A SIP Response Code for Unwanted Calls}},
    pagetotal = 6,
    year =      2016,
    month =     dec,
    day =       12,
    abstract =  {This document defines the 666 (Unwanted) SIP response code, allowing called parties to indicate that the call was unwanted. The terminating SIP entity may use this information to adjust future call handling behavior for this called party or more broadly.},
}