July 1, 1948.
Dear Miss Kann,
At Dr. Luria's request I am sending you the following cultures derived from K-12:
Y-10 Threonine, Leucine, Thiamin -- (T-L-B1-)
Y-87 Biotin, Methionine -- (B-M-) and Lac1-V1r
58-161 Simply B-K-.
These cultures are referred to in detail in my paper in Genetics, 32:505.
Luria implied that you might have some new single mutants of K-12.  Is this the case?
Let me know if you have any difficulty in making "crosses".  There should be none.
Yours sincerely,
Joshua Lederberg
Assistant Professor of Genetics.