Dear______,
I am writing to extend my sincere gratitude for _________ (感谢的`原因). If it had not been for your assistance in ___________ (对方给你的具体帮助), I fear that I would have been_________(没有对方帮助时的后果).
Every one agrees that it was you who______________(给出细节)n, I would like to express my warm thanks to you! Please accept my gratitude.
Yours sincerely
Li Ming