exchange of letters

商务英语词汇大全_外语教育网 ... collection 收信 exchange of letters 书信往来 acknowledgement of receipt 回执 ...

in exchange for ... exchange of know-how 技术交流 exchange of letters 换函 exchange of ratification 交换批准书 ...

...盟约(covenant)、规约(statute)、换文（exchange of letters）、 宣言（proclamation）等。