public static function fetch( $attributeId, $version, $asObject = true )
    {
        $list = eZPersistentObject::fetchObjectList( 
                                        self::definition(),
                                        null,
                                        array( 'contentobject_attribute_id' => $attributeId, 'contentobject_version' => $version  ), 
                                        null,
                                        null,
                                        $asObject
                );
        if ( isset( $list[0] ) )
            return $list[0];
        return null;
    }