All the characters in a reference reserved name, used because no replacement for it is specified in the general delimiters parameter of the SGML Declaration, must be mapped to unique document characters.
          #0200   Markup Error
ISO 8879, 13.1
          All the characters in a reference reserved name, used because no replacement for it is specified in the general delimiters parameter of the SGML Declaration, must be mapped to unique document characters.