%% You should probably cite draft-ietf-sipcore-reason-q850-loc instead of this I-D.
@techreport{sipcore-reason-q850-loc-00,
    number =    {draft-sipcore-reason-q850-loc-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-sipcore-reason-q850-loc/00/},
    author =    {Roland Jesske},
    title =     {{ISUP Cause Location Parameter for the SIP Reason Header Field}},
    pagetotal = 5,
    year =      2017,
    month =     may,
    day =       16,
    abstract =  {The SIP Reason header field is defined for carrying ISUP cause values as well as SIP response codes. Some services in SIP networks may need to know the ISUP location where the call was released in the PSTN network to correctly interpret the reason of release.},
}