%% You should probably cite rfc8262 instead of this I-D. @techreport{ietf-sipcore-content-id-04, number = {draft-ietf-sipcore-content-id-04}, 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-content-id/04/}, author = {Christer Holmberg and Ivo Sedlacek}, title = {{Content-ID header field in Session Initiation Protocol (SIP)}}, pagetotal = 9, year = 2017, month = may, day = 8, abstract = {This document specifies the Content-ID header field for usage in the Session Initiation Protocol (SIP). The document also updates RFC 5621, to enable a Content-ID URL to reference a complete message-body and metadata provided by some additional SIP header fields.}, }