Thank you for your letter.

Thank you for your recent letter in reply to mine of 15th May.

Thank you for your letter giving further information about this application.

Thank you for your letter of the 17th February 19.concerning.

'Thank you for your letter which is very interesting indeed, to say the least,' he wrote.

Thank you for your letter of 9 May, and the enclosures.

Thank you for your recent letter, which I have just received.

Thank you for your letter regarding the above which was received on 20th August 1993.

Thank you for your letter of the 27 October 1992 in connection with the above.

Thank you for your letter of 18 September regarding the above.

It is a proper time to thank you for your letter.