Elements that may be used, along with data characters inside the content model of the <compound-subject-part> element
<!ENTITY % compound-subject-part-elements "| %emphasis.class; | %inline-display.class; | %inline-math.class; | %phrase-content.class; | %subsup.class;" >
| bold | fixed-case | italic | monospace | overline | overline-start | overline-end | roman | sans-serif | sc | strike | underline | underline-start | underline-end | ruby | alternatives | inline-graphic | private-char | chem-struct | inline-formula | named-content | styled-content | sub | sup