private function writeComment(XMLWriter $objWriter, $pCellReference, Comment $pComment, array $pAuthors)
    {
        // comment
        $objWriter->startElement('comment');
        $objWriter->writeAttribute('ref', $pCellReference);
        $objWriter->writeAttribute('authorId', $pAuthors[$pComment->getAuthor()]);

        // text
        $objWriter->startElement('text');
        $this->getParentWriter()->getWriterPart('stringtable')->writeRichText($objWriter, $pComment->getText());
        $objWriter->endElement();

        $objWriter->endElement();
    }