a. fill a vacancy caused by the resignation, without the consent of the Tribunal, of an arbitrator appointed by a party, or

b. at the request of either party, fill any other vacancy, if no new appointment is made and accepted within 30 days of the notification of the vacancy by the Secretary-General.

(3) In filling a vacancy the party or the Secretary-General, as the case may be, shall observe the provisions of these Rules with respect to the appointment of arbitrators. Article 14(2) of these Rules shall apply mutatis mutandis to the newly appointed arbitrator.

Article 19