Dear ______ ,
①I am writing to extend my sincere gratitude for ______(感谢的原因). ②If it had not been for your assistance in ______(对方给予的具体帮助), I fear that I would have been ______(没有对方帮助时的后果).
③Every one agrees that it was you who ______(给出细节).
④Again, I would like to express my warm thanks to you! Please accept my gratitude.