December 16, 1968

Dr. K. A. Youssef
37 Str. El Asr El Aini (Apt. 5)
Cairo, Egypt

Dear Dr. Youssef:
I thank you for your letter of December 7.

I am not actively engaged in work on bacterial cytology at the present

time. For this reason I think you would do better to communicate with

some of the established authorities in the field, for example, Dr. John
Cairns at the Cold Spring Harbor Laboratory, and Dr. M. E. Bayer at the
Institute for Cancer Research, Philadelphia, Pennsylvania.

Sincerely yours,

Joshua Lederberg
Professor of Genetics

a