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.
Rosell, Marianne; Ljungqvist, Arne; Åhgren, Åsa, eds. (1992). Försvarets radioanstalt 50 år: 1942–1992 [Defence Radio Establishment 50 years: 1942–1992] (PDF) (in Swedish). Bromma: Försvarets radioanstalt (FRA). p. 27. SELIBR1499703. Archived from the original(PDF) on 11 March 2016. Retrieved 24 February 2016.
semanticscholar.org
api.semanticscholar.org
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.
signalspaning.se
Rosell, Marianne; Ljungqvist, Arne; Åhgren, Åsa, eds. (1992). Försvarets radioanstalt 50 år: 1942–1992 [Defence Radio Establishment 50 years: 1942–1992] (PDF) (in Swedish). Bromma: Försvarets radioanstalt (FRA). p. 27. SELIBR1499703. Archived from the original(PDF) on 11 March 2016. Retrieved 24 February 2016.