Used to mark text that should remain in roman script no matter what style the surrounding text takes on.
<!ELEMENT roman (#PCDATA %emphasized-text;)* >
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Any combination of:
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... <sec> <title>Seasonal Variations of <roman>CO</roman>, <roman>N<sub>2</sub>O</roman>, and <roman>CO<sub>2</sub></roman></title> <p>Recent evidence supports the premise that concentrations of major greenhouse gases vary ...</p> ... </sec> ...
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