public function getListElements( core_kernel_classes_Class $listClass, $sort = true)
    {
        $returnValue = array();

    	if($sort){
        	$levelProperty = new core_kernel_classes_Property(TaoOntology::PROPERTY_LIST_LEVEL);
        	foreach ($listClass->getInstances(false) as $element) {
        	    $literal = $element->getOnePropertyValue($levelProperty);
        	    $level = is_null($literal) ? 0 : (string) $literal;
        	    while (isset($returnValue[$level])) {
        	        $level++;
        	    }
        	    $returnValue[$level] = $element;
        	}
			uksort($returnValue, 'strnatcasecmp');
    	}
    	else{
    		$returnValue = $listClass->getInstances(false);
    	}

        return (array) $returnValue;
    }