[BCP77]    Best Current Practice 77,
              <https://www.rfc-editor.org/info/bcp77>.
              At the time of writing, this BCP comprises the following:

              Daigle, L., Ed. and IAB, "IETF ISOC Board of Trustee
              Appointment Procedures", BCP 77, RFC 3677,
              DOI 10.17487/RFC3677, December 2003,
              <https://www.rfc-editor.org/info/rfc3677>.