SharePoint 2013 Crossdomainrequest Listitem Username zur UserID

Ich versuche aus einer SharePoint Liste Personen zu bekommen.
Alles was ich bisher aber habe sind bloß die IDs zu den Personen.

UserId: {
     [functions]: ,
     __metadata: { },
     results: [
        0: 1,
        1: 9,
        2: 10,
        3: 11,
        4: 21,
        length: 5
     ]
  }

Wie bekomme ich die Namen zu diesen IDs?

function execCrossDomainRequest() {
    var executor = new SP.RequestExecutor(appweburl);
    var listguid = 'EB385857-61A5-40F2-84A2-59A6965CE4B6';  
    var url = appweburl + "/_api/SP.AppContextSite(@target)/web/lists(guid'" + listguid + "')/items?" + "@target='" + hostweburl + "'"; //use guid of list to make sure there are no errors  
    var requestHeader = { "Accept": "application/json; odata=verbose" };  

    executor.executeAsync({
        url: url,
        method: "GET",  
        headers: requestHeader,
        success: successGet,
        error: failedRequest
    });
}

function successGet(data) {
    var jsonObject = JSON.parse(data.body);
    var results = jsonObject.d.results;
    log(results);
}