Frisch–Peierls memorandum
The Frisch–Peierls memorandum was the first technical exposition of a practical nuclear weapon. It was written by expatriate German-Jewish physicist Rudolf Peierls and Austrian-Jewish physicist Otto Frisch in March 1940 while they were both working for Mark Oliphant at the University of Birmingham in Britain during World War II. The memorandum contained some of the first calculations about the size of the critical mass of fissile material needed for an atomic bomb.
Source: Wikipedia — Frisch–Peierls memorandum (CC BY-SA 4.0)