private int numDatalinks() {
    int numDL = 0 ; for (Item i : stocks.matches(DATALINKS)) {
      if (i.refers instanceof Skill) numDL++ ;
    }
    for (Manufacture m : stocks.specialOrders()) {
      if (m.conversion.out.type == DATALINKS) numDL++ ;
    }
    return numDL ;
  }