The <h9> tag
<h9>
When exporting to ODT, novelibre converts this to “Heading 9”.
The xml:lang attribute
The optional locale is for ODF document spell check control.
The attribute has the form <Language code> or
<Language code>-<Country code>,
where the language code is according to ISO 639-1,
and the optional country code is according to ISO 3166-2.
Example: en-GB is for British English.