Content Model

<!ENTITY % sig-block-elements 
                         "| %break.class; | %emphasis.class; |   
                          %just-base-display.class; |
                          %inline-display-noalt.class; |
                          %phrase-content.class; | 
                          %sig.class; | %subsup.class;"              >

Expanded Content Model

| break | bold | italic | monospace | overline | overline-start | overline-end | roman | sans-serif | sc | strike | underline | underline-start | underline-end | alternatives | graphic | media | inline-graphic | private-char | named-content | styled-content | sig | sub | sup