[BCP46]    Best Current Practice 46,
              <https://www.rfc-editor.org/info/bcp46>.
              At the time of writing, this BCP comprises the following:

              Killalea, T., "Recommended Internet Service Provider
              Security Services and Procedures", BCP 46, RFC 3013,
              DOI 10.17487/RFC3013, November 2000,
              <https://www.rfc-editor.org/info/rfc3013>.