%% You should probably cite rfc5368 instead of this I-D.
@techreport{ietf-sip-multiple-refer-03,
    number =    {draft-ietf-sip-multiple-refer-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-ietf-sip-multiple-refer/03/},
    author =    {Markus Isomaki and Gonzalo Camarillo and Hisham Khartabil and Aki Niemi and Miguel Angel García},
    title =     {{Referring to Multiple Resources in the Session Initiation Protocol (SIP)}},
    pagetotal = 13,
    year =      2007,
    month =     dec,
    day =       18,
    abstract =  {This document defines extensions to the SIP REFER method so that it can be used to refer to multiple resources in a single request. These extensions include the use of pointers to Uniform Resource Identifier (URI) lists in the Refer-To header field and the "multiple-refer" SIP option-tag. {[}STANDARDS-TRACK{]}},
}