/**
  * Get billing history
  *
  * @param card
  * @param limit
  * @param start
  * @return
  */
 public String getHistory(Card card, Integer limit, Integer start) {
   this.currentCard = card;
   JSONObject json = new JSONObject();
   List<Invoice> history = invoiceService.getIncome(currentCard);
   history.addAll(invoiceService.getOutcome(currentCard));
   try {
     json.put("total", history.size());
     for (int i = start; i <= start + limit && i < history.size(); i++) {
       json.accumulate("history", history.get(i).toJson());
     }
   } catch (JSONException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
   }
   return json.toString();
 }