Avoid as far as possible full-dress compounds of this kind unless, like therefore, they have become part of every-day language. Most of them put a flavour of legalism into any document in which they are used. Use a preposition and pronoun instead.
With reference to the second paragraph thereof. (With reference to its second paragraph.)
I have received your letter and thank you for the information contained therein. (I thank you for the information contained in your letter.)
I am to ask you to explain the circumstances in which the gift was made and to forward any correspondence relative thereto. (. . . any correspondence about it.)
Do not say "I enclose herewith". Herewith adds nothing to the sense. All it does is to put a touch of starch into the letter.