private function print_restoreversion() {
        global $OUTPUT;

        $version = wiki_get_version($this->version->id);

        $optionsyes = array('confirm'=>1, 'pageid'=>$this->page->id, 'versionid'=>$version->id, 'sesskey'=>sesskey());
        $restoreurl = new moodle_url('/mod/wiki/restoreversion.php', $optionsyes);
        $return = new moodle_url('/mod/wiki/viewversion.php', array('pageid'=>$this->page->id, 'versionid'=>$version->id));

        echo $OUTPUT->container_start();
        echo html_writer::tag('div', get_string('restoreconfirm', 'wiki', $version->version));
        echo $OUTPUT->container_start(false, 'wiki_restoreform');
        echo '<form class="wiki_restore_yes" action="' . $restoreurl . '" method="post" id="restoreversion">';
        echo '<div><input type="submit" class="btn btn-secondary" name="confirm" value="' . get_string('yes') . '" /></div>';
        echo '</form>';
        echo '<form class="wiki_restore_no" action="' . $return . '" method="post">';
        echo '<div><input type="submit" class="btn btn-secondary" name="norestore" value="' . get_string('no') . '" /></div>';
        echo '</form>';
        echo $OUTPUT->container_end();
        echo $OUTPUT->container_end();
    }