^Lieutenant Commander James T. Westwood, USN. Electronic Warfare and Signals Intelligence at the Outset of World War I(PDF). NSA. [2009-05-04]. (原始内容(PDF)存档于5 August 2012). After the war, it was estimated that Room 40 had solved some 15,000 German naval and diplomatic communications, a very great number considering that recoveries were hand-generated.
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