New York June the 15th
Dear Dr. Lederberg,
I now spend a few weeks in the States and shall be next week in Chicago and Urbana.  I should be very glad to visit you in Madison if you have some hours free.  The easier for me should be in the beginning of the next week.  Could you give me your answer c/o J? Novick, Chicago.  I hope it will be possible for me to come to your lab without too much disturbance for you, and I shall be very glad to meet you.
Sincerely yours
Francois Jacob
(from Pasteur Institute)