Well, the drawback of these documents is that a purchase order for a supplier, and they bring us the partial units, one makes a sales invoice associates the purchase order once with the purchase invoice, for example (if 100 units were requested and 60 UND arrived first) one assumes that the order will be left with the balance of 40 UND but it says support that no, the purchase order can only be used once, so if we would like both the purchase order and sale to be handled the issue of order balances and one can associate with several invoices. I think that several companies have in their processes that issue a purchase order to their supplier, tell them on the invoice they tell me what the purchase order is, the supplier can issue 2, 3 or invoices or make a monthly invoice associating that order, but the system is very closed in that part