[BCP21]    Best Current Practice 21,
              <https://www.rfc-editor.org/info/bcp21>.
              At the time of writing, this BCP comprises the following:

              Brownlee, N. and E. Guttman, "Expectations for Computer
              Security Incident Response", BCP 21, RFC 2350,
              DOI 10.17487/RFC2350, June 1998,
              <https://www.rfc-editor.org/info/rfc2350>.