[STD24]    Internet Standard 24,
              <https://www.rfc-editor.org/info/std24>.
              At the time of writing, this STD comprises the following:

              Postel, J., "Active users", STD 24, RFC 866,
              DOI 10.17487/RFC0866, May 1983,
              <https://www.rfc-editor.org/info/rfc866>.