Dear Prof. Smith,
Many thanks for your hospitability and the honor you showed me during my recent visit to your country. It was thoughtful of you to introduce me to so many of your famous professors and learned scholars in your Country. ?I have learned a lot from them. I returned to China safe and sound last Friday, and have resumed my work now.
I hope you will some day visit our country with its ancient history and beautiful scenery, and give us some lectures on "Modern English ?Literature".
Please have no hesitation in writing to me should you want me to do something for you in China.
With best wishes, I remain.（祝好）
Yours sincerely,
David Li