The importance of the documentation provided by customs is clear in that it provides evidence of export. The importance of the documentation validated by third country authorities arises from the way in which the Commission has differentiated refund rates for many products by final destination. Thus varying rates of refund are payable for the export of the same product depending upon the country of import. The checking of evidence of arrival for destinations which attract high rates of refund is therefore particularly important. As has already been explained to the Court's representatives on several occasions, the correctives are an integral part of the refund. They are additions to or deductions from the refunds fixed for each month of delivery during the period of the export licence's validity. The correctives apply both to ordinary (basic) refunds and to the (basic) refunds fixed by tendering procedure. Their purpose may be to encourage exports to a specific destination or to reflect price fluctations on the world futures market, so that a correspondingly differentiated refund (basic amount + corrective) is granted for each month of delivery. Positive or negative correctives may be fixed, where necessary for a particular destination. This is done to ensure that all the cereals are delivered within the period of the export licence's validity.