[BCP67]    Best Current Practice 67,
              <https://www.rfc-editor.org/info/bcp67>.
              At the time of writing, this BCP comprises the following:

              Peterson, J., Jennings, C., and R. Sparks, "Change Process
              for the Session Initiation Protocol (SIP) and the Real-
              time Applications and Infrastructure Area", BCP 67,
              RFC 5727, DOI 10.17487/RFC5727, March 2010,
              <https://www.rfc-editor.org/info/rfc5727>.

              Campbell, B., Ed., Cooper, A., and B. Leiba, "DISPATCH-
              Style Working Groups and the SIP Change Process", BCP 67,
              RFC 7957, DOI 10.17487/RFC7957, August 2016,
              <https://www.rfc-editor.org/info/rfc7957>.