(b) This Agreement may be modified or modified with respect to a Pledgor only by a written agreement executed by such Pledgor and the secured creditor or its successors, and any provision of this Agreement may not be waived, except for a written document of the party granting such waiver; Provided that the pledge holder may modify or modify this agreement in respect of a pledge holder without the written consent of that pledge holder, if such modification or modification (i) is not significantly prejudicial to that Pledgor and (ii) is necessary or desirable, following the judgment of an authorized creditor, to justify or enhance the security interest for the pledged securities, which is granted to this holder of guarantees of authorized prior. No Pledgor may assign, directly or indirectly, any such rights or obligations of Pledgor under this Agreement without the prior written consent of the secured creditor, his successors or such mandated persons, and such assignment by such Pledgor in breach of this Agreement shall not be valid. This Agreement is binding on all successors and authorized recipients of Pledgors. Without prejudice to Pledgors` obligations under this Agreement, the secured creditor may, at any time and from time to time, assign its rights and obligations under this Agreement to one of its subsidiaries or related enterprises (and cause such rights and obligations to be transferred to Pledgors or related companies, as well as to another subsidiary or related enterprise). This Agreement is binding on and to the benefit of the pledge holder and his successors and consignees of the assignment. . . .