private function _createReferencesSqlFunction(array $args)
	{
		$this->_checkSecondArgument($args);
		if(isset($args[2]) && !is_array($args[2]))
		{
			throw new \Exception('sql function references argument have to be an array or null!');
		}
		$argArray = (isset($args[2])) ? $args[2] : array();

		return new SqlFunction($args[1], $argArray);
	}