The European Communities submits that the 15 month period mentioned in Article 21.3（c） for the “reasonable period of time” is a “guideline” for the arbitrator, not an “average” or “usual” period. The European Communities argues that past arbitrations make clear that the “reasonable period of time” should be the shortest period of time possible within the legal system of the Member to implement the recommendations and rulings of the DSB. Article 21.3（c） refers to the notion of “particular circumstances” that can influence the “reasonable period of time”. The “particular circumstances” of each case determine the length of this period.