Lise Meitner, letters to Otto Hahn; Kopfermann to Bohr, in Klaus Hentschel and Ann M. Hentschel, Physics and National Socialism: An Anthology of Sources (1996).
Einstein's letter to Roosevelt (2 August 1939).
Decree No. 2352 cc of the State Committee of Defense, "On the Organization of Work on Uranium" (28 September 1942).
Alan Beyerchen, Scientists under Hitler.
P. Josephson, Yu. Ranyuk, Yu. Tsekhmistro, and K. Hall, "Science and the periphery under Stalin: Physics in Ukraine," in Trischler and Walker, Physics and Politics Research and Research Support in Twentieth Century Germany in International Perspective (2010), 197-226.
David Holloway, "Nuclear prehistory," Stalin and the Bomb, chapter 2.
Graetzer and Anderson, The Discovery of Nuclear Fission: A Documentary History (1971). [excerpts in file below]