%c is only allowed in a rule of type ELEMENT, DATA-CONTENT, MARKED-SECTION IGNORE, MARKED-SECTION CDATA, MARKED-SECTION RCDATA, and MARKUP-COMMENT or in the body of a DO SGML-PARSE or DO XML-PARSEaction. Any use of it in other contexts is an error.
ELEMENT
DATA-CONTENT
MARKED-SECTION IGNORE
MARKED-SECTION CDATA
MARKED-SECTION RCDATA
MARKUP-COMMENT
DO SGML-PARSE
DO XML-PARSE