THE ARBITRATION RULES OF CHICAGO INTERNATIONAL DISPUTE RESOLUTION ASSOCIATION (CIDRA) ARTICLE 13 - PROCEDURES FOR CHALLENGE 1) A party who intends to challenge an arbitrator shall send notice of his challenge within fifteen days after the appointment of the challenged arbitrator has been notified to CIDRA or within fifteen days after the circumstances mentioned in Articles 11 and 12 became known to that party. 2) The party making the challenge shall notify CIDRA and the other party of that challenge. The notification shall be in writing and shall state the reasons for the challenge. 3) When an arbitrator has been challenged by one party, the other party may agree to the challenge. In both cases the procedure provided in Article 8 or 9 shall be used in full for the appointment of the substitute arbitrator, even if during the process of appointing the challenged arbitrator a party had failed to exercise his right to appoint or to participate in the appointment.