sing</a>
     are any
     <a href="syntax.html#syntax-elements">elements</a>,
     <a href="syntax.html#character-data" id="character-data_xref2">character data</a>,
     <a href="syntax.html#syntax-comments" id="syntax-comments_xref6">comments</a>,
     and
     <a href="syntax.html#syntax-cdata-sections" id="syntax-cdata-sections_xref1">CDATA sections</a>
     that it contains, with the restriction
     that any 
     <a href="syntax.html#character-data" id="character-data_xref3">character data</a>
     