How to get custom label field from eBay API?

I am having trouble with custom lable field from ebay API. I can get all values escept custom field. This is my code:

$s_endpoint = 'http://open.api.ebay.com/shopping'; 
$apicall = $f_endpoint
            ."?OPERATION-NAME=findItemsIneBayStores"
            ."&SERVICE-VERSION=".$f_version
            . "&SECURITY-APPNAME=".$appID
            . "&RESPONSE-DATA-FORMAT=XML"
            . "&REST-PAYLOAD"
            . "&storeName=".$sellerID
            . "&outputSelector=StoreInfo";

This is custom lable field.

Could you give me the advise to resolve this problem.