public function getScriptID($id)
	{
		// normalize id
		$id = $this->getCanonicalID($id);
		// find sub tags
		if(($underscorePosition=strpos($id, '_'))!==false)
		{
			$subTag = explode('_', $id);
			// script sub tags can be distinguished from territory sub tags by length
			if (strlen($subTag[1])===4)
			{
				$id = $subTag[1];
			}
			else
			{
				$id = null;
			}
		}
		else
		{
			$id = null;
		}
		return $id;
	}