[STD55]    Internet Standard 55,
              <https://www.rfc-editor.org/info/std55>.
              At the time of writing, this STD comprises the following:

              Brown, C. and A. Malis, "Multiprotocol Interconnect over
              Frame Relay", STD 55, RFC 2427, DOI 10.17487/RFC2427,
              September 1998, <https://www.rfc-editor.org/info/rfc2427>.