108Admittedly, it follows from Articles 13(5) and 14(3) of the basic regulation and from Article 26(1) of the Community customs code that the Community institutions may introduce specific rules in relation to the documents that importers must be able to produce in order to show that the goods concerned have a non-preferential origin. However, the parties are agreed that before the entry into force of the regulation extending the duty no such specific rules had been adopted.