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). Again, I would like to express my warm thanks to you! please accept my gratitude.
Yours sincerely
Li Ming