1. If the parties have not agreed on the number of arbi­tra­tors, the number shall be determined by the Administrator after the filing of the short answer or, in the absence there­of, after expiration of the period of time for filing the short answer.

2. The Administrator shall determine that the number of arbi­trators be one or three, taking into account the prefe­rence of the parties, the amount of the claim and of the counterclaim, if any, and the complexity of the case.

3. If the parties agreed on an even number of arbitrators, the latter shall appoint an additional arbitrator who shall act as the chairman of the arbitral tribunal. If, within two weeks * after acceptance of their mandate, the arbitra­tors fail to agree on the additional arbitrator, the latter shall, at the request of either party, be appointed in accordance with the list-procedure provided in article 14.

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