The European Commission and OCCAR have signed contribution agreements for the management and implementation of two European Defence Industrial Development Programmes (EDIDP) The right to commission does not apply when a concluded transaction is not carried out in whole or in part, if and to the extent that this is due to circumstances not represented by the contracting authority. The commission rates and the calculation bases for the calculation of the commission referred to in the preceding paragraphs may only be modified by contract. No ancillary agreements have been concluded under this contract. The amendments necessary for their validity shall be those signed by both Contracting Parties. This request for a trainer may only be abandoned by written agreement.  The right to commission is subject to the conclusion of the transaction during the existing commercial agent contract, regardless of the date of execution of the transaction by the procuring entity. . . .