%% You should probably cite rfc6993 instead of this I-D. @techreport{saintandre-impp-call-info-03, number = {draft-saintandre-impp-call-info-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-saintandre-impp-call-info/03/}, author = {Peter Saint-Andre}, title = {{Instant Messaging and Presence Purpose for the Call-Info Header Field in the Session Initiation Protocol (SIP)}}, pagetotal = 5, year = 2013, month = may, day = 14, abstract = {This document defines and registers a value of "impp" ("instant messaging and presence protocol") for the "purpose" header field parameter of the Call-Info header field in the Session Initiation Protocol (SIP).}, }