[STD52]    Internet Standard 52,
              <https://www.rfc-editor.org/info/std52>.
              At the time of writing, this STD comprises the following:

              Piscitello, D. and J. Lawrence, "The Transmission of IP
              Datagrams over the SMDS Service", STD 52, RFC 1209,
              DOI 10.17487/RFC1209, March 1991,
              <https://www.rfc-editor.org/info/rfc1209>.