SP Online (Form): Text Field with Autocomplete (Values from a SP List Column)

Hello Nintex Community!

Hopefully someone can help me out with this:

1. Downloaded SPServices from http://spservices.codeplex.com/
2. Modified the jquery.SPServices-2014.02.min.js (Changed "(jQuery)" to "(NWF$)")
3. Uploaded the modified jquery.SPServices-2014.02.min.js with the SP Designer to the "Style Library"
4. Set the Client ID JavaScript variable name of the Text Field to myCity
5. Added the path to the jquery.SPServices-2014.02.min.js in Custom JavaScript Includes
6. Added the following Code to Custom JavaScript
   

NWF$(document).ready(function() {

var itemSource = [];
var i = 0;

NWF$().SPServices({
  operation: "GetListItems",
  async: false,
  listName: "myCityList",
  CAMLViewFields: '<ViewFields><FieldRef/></ViewFields>',
  CAMLQuery: '<Query><OrderBy><FieldRef Name='City' Ascending='True' /></OrderBy></Query>',
  completefunc: function(xData, Status) {
   NWF$(xData.responseXML).find("[nodeName= z:row]").each(function() {
    itemSource = NWF$(this).attr('ows_City');
    i = i + 1;
   });
  }
});

NWF$("#" + myCity).autocomplete({     
   source: itemSource 
   });
});

The internal Field Name of the column City is City.

What am I missing?

Thanks in advance & kind regards,
Milan