求翻译：The party which is unable to fulfill its obligations under the present contract must within 15 days of occurrence of any of the causes mentioned in this clause shall inform the other party of the existence of the termination of the circumstances preventing the performance of the contract. Certificate issued by a Chamber of Commerce or any other competent authority connected with the cause in the country of the Seller or the buyer shall be sufficient proof of the existence of the above circumstances and their duration. Non-availability of material will not be an excuse to the Sellers for not performing their obligations under this contract.是什么意思？

待解决 悬赏分：1 - 离问题结束还有