Find CHILD_WORK_ITEMS in a Follow up (extends AbstractService implements IOperationParticipant)

Hello,

I need find CHILD_WORK_ITEMS ...(only by AbstractService )

I am trying this code:

IWorkItemReferences ref= workItemServer.resolveWorkItemReferences((IWorkItemHandle)workItem, monitor);


if(ref.hasReferences(WorkItemEndPoints.CHILD_WORK_ITEMS)){


                 List<IReference>  listChildReferences = ref.getReferences(WorkItemEndPoints.CHILD_WORK_ITEMS);     //Always listChildReferences.size()=0..???
                             
   //no works                                      
                 for (IReference reference: listChildReferences){
                                  
                        //get wi child id
            //find wi by id
                 }
} 

===========

List<IEndPointDescriptor> auxList= ref.getTypes(); //ONLY i can extract the display names....I need the wi child objects...

thanks