@Override
	public void removeStock(Stock stock) {
		tx.begin();
		for (SubProcess sp : stock.getSubProcesses()) {
			stock.removeSubProcess(sp);
		}
		for (StorageUnit su : stock.getStorageUnits()) {
			stock.removeStorageUnit(su);
		}
		em.merge(stock);
		em.remove(stock);
		tx.commit();
	}