public function createContentFile($worksheets, $styleHelper)
    {
        $contentXmlFileContents = <<<EOD
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<office:document-content office:version="1.2" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:calcext="urn:org:documentfoundation:names:experimental:calc:xmlns:calcext:1.0" xmlns:draw="urn:oasis:names:tc:opendocument:xmlns:drawing:1.0" xmlns:fo="urn:oasis:names:tc:opendocument:xmlns:xsl-fo-compatible:1.0" xmlns:msoxl="http://schemas.microsoft.com/office/excel/formula" xmlns:number="urn:oasis:names:tc:opendocument:xmlns:datastyle:1.0" xmlns:office="urn:oasis:names:tc:opendocument:xmlns:office:1.0" xmlns:style="urn:oasis:names:tc:opendocument:xmlns:style:1.0" xmlns:svg="urn:oasis:names:tc:opendocument:xmlns:svg-compatible:1.0" xmlns:table="urn:oasis:names:tc:opendocument:xmlns:table:1.0" xmlns:text="urn:oasis:names:tc:opendocument:xmlns:text:1.0" xmlns:xlink="http://www.w3.org/1999/xlink">
EOD;

        $contentXmlFileContents .= $styleHelper->getContentXmlFontFaceSectionContent();
        $contentXmlFileContents .= $styleHelper->getContentXmlAutomaticStylesSectionContent(count($worksheets));

        $contentXmlFileContents .= '<office:body><office:spreadsheet>';

        $this->createFileWithContents($this->rootFolder, self::CONTENT_XML_FILE_NAME, $contentXmlFileContents);

        // Append sheets content to "content.xml"
        $contentXmlFilePath = $this->rootFolder . '/' . self::CONTENT_XML_FILE_NAME;
        $contentXmlHandle = fopen($contentXmlFilePath, 'a');

        foreach ($worksheets as $worksheet) {
            // write the "<table:table>" node, with the final sheet's name
            fwrite($contentXmlHandle, $worksheet->getTableElementStartAsString());

            $worksheetFilePath = $worksheet->getWorksheetFilePath();
            $this->copyFileContentsToTarget($worksheetFilePath, $contentXmlHandle);

            fwrite($contentXmlHandle, '</table:table>');
        }

        $contentXmlFileContents = '</office:spreadsheet></office:body></office:document-content>';

        fwrite($contentXmlHandle, $contentXmlFileContents);
        fclose($contentXmlHandle);

        return $this;
    }