[BCP27]    Best Current Practice 27,
              <https://www.rfc-editor.org/info/bcp27>.
              At the time of writing, this BCP comprises the following:

              O'Dell, M., Alvestrand, H., Wijnen, B., and S. Bradner,
              "Advancement of MIB specifications on the IETF Standards
              Track", BCP 27, RFC 2438, DOI 10.17487/RFC2438, October
              1998, <https://www.rfc-editor.org/info/rfc2438>.