(1) After a Tribunal has been constituted and proceedings have begun, its composition shall remain unchanged; provided, however, that if an arbitrator should die,become incapacitated,resign or be dis- qualified,the resulting vacancy shall be filled as provided in this Article and
(2) Ifan arbitrator becomes incapacitated or unable to perform the duties of his office, the procedure in respect of the disqualification of arbitrators set forth in
(3) An arbitrator may resign by submitting his resignation to the other members of the Tribunal and the Secretary-General.If the arbi- trator was appointed by one of the parties, the Tribunal shall promptly consider the reasons for his resignation and decide whether it consents thereto.The Tribunal shall promptly notify the Secretary- General of its decision.