I also recommend Venona^, it has close to a hundred pages of notes on the decoded cables plus the authors had brief access to Soviet records. ^ Haynes, John E

I also recommend Venona^, it has close to a hundred pages of notes on the decoded cables plus the authors had brief access to Soviet records. ^ Haynes, John Earl & Klehr, Harvey (2000). Venona: Decoding Soviet Espionage in America. Yale University Press. ISBN 978-0-300-08462-7 https://yalebooks.yale.edu/book/9780300084627/venona https://yalebooks.yale.edu/book/9780300084627/venona