Aid, Matthew (September 2002). Stella Polaris and the secret code battle in postwar Europe. Journal of Intelligence and National Security. 17 (3): 17—86. doi:10.1080/02684520412331306550. S2CID153619850.
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Aid, Matthew (September 2002). Stella Polaris and the secret code battle in postwar Europe. Journal of Intelligence and National Security. 17 (3): 17—86. doi:10.1080/02684520412331306550. S2CID153619850.