[BCP140]   Best Current Practice 140,
              <https://www.rfc-editor.org/info/bcp140>.
              At the time of writing, this BCP comprises the following:

              Damas, J. and F. Neves, "Preventing Use of Recursive
              Nameservers in Reflector Attacks", BCP 140, RFC 5358,
              DOI 10.17487/RFC5358, October 2008,
              <https://www.rfc-editor.org/info/rfc5358>.