public static function nonPatentLiterature($text, $citedBy = null, $country = null, $citationDate = null)
{
$citation = new Citation(Citation::NON_PATENT_LITERATURE);
$citation->setText($text);
$citation->setCitedBy($citedBy);
$citation->setCitationDate($citationDate);
$citation->setCountry($country);
return $citation;
}