呼语： 特定的写信对象：dear xx
不明确收信人：dear sir/madam， or to whom it may concern
i am writing to express my heartfelt gratitude. i am referring to that unfortunate accident the other day， when i was knocked off my bike by a taxi.
if it had not been for your timely assistance in giving me first aid， i fear that the consequences might have been much more serious. everyone agrees that it was your quick-witted response in that emergency that has led to this satisfactory outcome.
although nowadays people in mounting numbers talk about the need to be unselfish， we see very few people practice what they preach. if there were more people like you， this world would be a much nicer place.
if it had not been for your timely…， i fear that agrees that it quick-witted a much nicer place.