public function generateHTMLHeader($pIncludeStyles = false)
    {
        // PHPExcel object known?
        if (is_null($this->phpExcel)) {
            throw new PHPExcel_Writer_Exception('Internal PHPExcel object not set to an instance of an object.');
        }

        // Construct HTML
        $properties = $this->phpExcel->getProperties();
        $html = '<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">' . PHP_EOL;
        $html .= '<!-- Generated by PHPExcel - http://www.phpexcel.net -->' . PHP_EOL;
        $html .= '<html>' . PHP_EOL;
        $html .= '  <head>' . PHP_EOL;
        $html .= '      <meta http-equiv="Content-Type" content="text/html; charset=utf-8">' . PHP_EOL;
        if ($properties->getTitle() > '') {
            $html .= '      <title>' . htmlspecialchars($properties->getTitle()) . '</title>' . PHP_EOL;
        }
        if ($properties->getCreator() > '') {
            $html .= '      <meta name="author" content="' . htmlspecialchars($properties->getCreator()) . '" />' . PHP_EOL;
        }
        if ($properties->getTitle() > '') {
            $html .= '      <meta name="title" content="' . htmlspecialchars($properties->getTitle()) . '" />' . PHP_EOL;
        }
        if ($properties->getDescription() > '') {
            $html .= '      <meta name="description" content="' . htmlspecialchars($properties->getDescription()) . '" />' . PHP_EOL;
        }
        if ($properties->getSubject() > '') {
            $html .= '      <meta name="subject" content="' . htmlspecialchars($properties->getSubject()) . '" />' . PHP_EOL;
        }
        if ($properties->getKeywords() > '') {
            $html .= '      <meta name="keywords" content="' . htmlspecialchars($properties->getKeywords()) . '" />' . PHP_EOL;
        }
        if ($properties->getCategory() > '') {
            $html .= '      <meta name="category" content="' . htmlspecialchars($properties->getCategory()) . '" />' . PHP_EOL;
        }
        if ($properties->getCompany() > '') {
            $html .= '      <meta name="company" content="' . htmlspecialchars($properties->getCompany()) . '" />' . PHP_EOL;
        }
        if ($properties->getManager() > '') {
            $html .= '      <meta name="manager" content="' . htmlspecialchars($properties->getManager()) . '" />' . PHP_EOL;
        }

        if ($pIncludeStyles) {
            $html .= $this->generateStyles(true);
        }

        $html .= '  </head>' . PHP_EOL;
        $html .= '' . PHP_EOL;
        $html .= '  <body>' . PHP_EOL;

        return $html;
    }