我非常愉快地回覆您1998年8月18日的來函查詢。
We are pleased to respond to your inquiry of August 18, 1998.
We are pleased to answer your letter of August 18, 1998.
以下是就您1998年10月21日來信的回函。
We are writing in response to your letter of October 21, 1998.
We are writing with reference to your letter of October 21, 1998.
這是對您1998年10月29日來信的`覆函。
This refers to your letter of October 29, 1998.
這是對您1998年11月4日來信給予的答覆。
This is in response to your letter of November 4, 1998.
