[BCP174]   Best Current Practice 174,
              <https://www.rfc-editor.org/info/bcp174>.
              At the time of writing, this BCP comprises the following:

              Huston, G., Michaelson, G., and S. Kent, "Certification
              Authority (CA) Key Rollover in the Resource Public Key
              Infrastructure (RPKI)", BCP 174, RFC 6489,
              DOI 10.17487/RFC6489, February 2012,
              <https://www.rfc-editor.org/info/rfc6489>.