[STD68]    Internet Standard 68,
              <https://www.rfc-editor.org/info/std68>.
              At the time of writing, this STD comprises the following:

              Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.