[BCP103]   Best Current Practice 103,
              <https://www.rfc-editor.org/info/bcp103>.
              At the time of writing, this BCP comprises the following:

              Trowbridge, S., Bradner, S., and F. Baker, "Procedures for
              Handling Liaison Statements to and from the IETF",
              BCP 103, RFC 4053, DOI 10.17487/RFC4053, April 2005,
              <https://www.rfc-editor.org/info/rfc4053>.