A number or expression that is set higher than the baseline and slightly smaller, to act as a superior or superscript
<!ELEMENT sup (#PCDATA %emphasized-text;)* >
(#PCDATA | email | ext-link | uri | inline-supplementary-material | related-article | related-object | bold | italic | monospace | overline | roman | sc | strike | underline | alternatives | inline-graphic | chem-struct | inline-formula | abbrev | named-content | styled-content | fn | target | xref | sub | sup)*
Any combination of:
<addr-line>, <aff>, <article-title>, <attrib>, <bold>, <chapter-title>, <chem-struct>, <collab>, <comment>, <conf-theme>, <copyright-holder>, <copyright-statement>, <def-head>, <disp-formula>, <element-citation>, <ext-link>, <funding-statement>, <gov>, <inline-formula>, <inline-supplementary-material>, <institution>, <italic>, <kwd>, <license-p>, <mixed-citation>, <monospace>, <named-content>, <on-behalf-of>, <overline>, <p>, <part-title>, <preformat>, <product>, <related-article>, <related-object>, <roman>, <sc>, <series>, <source>, <std>, <strike>, <styled-content>, <sub>, <subtitle>, <sup>, <supplement>, <target>, <td>, <term>, <term-head>, <textual-form>, <th>, <title>, <trans-source>, <trans-title>, <underline>, <verse-line>, <xref>
An ordinary superscript:
... <p>...The recent discovery that Hfq is required for translation of the ς<sup>s</sup> subunit of RNA polymerase ... Template for synthesis of <sup>32</sup>P-labeled RNA primer (97RNA) was obtained ...</p> ...
As shown formatted above, a subscript and superscript in a “stacked ” arrangement:
...
<body>
<p>The <italic>Escherichia coli argU</italic> gene encodes a minor arginine
tRNA, tRNA<sup arrange="stack">Arg</sup><sub arrange="stack">UCU</sub>,
which corresponds to the rare codon AGA and possibly AGG ....</p>
...
</body>
...
format3.ent