German submarine U-640 (English Wikipedia)

Analysis of information sources in references of the Wikipedia article "German submarine U-640" in English language version.

refsWebsite

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1books.google.com

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books.google.com

Gröner 1991, pp. 43–46. Gröner, Eric; Jung, Dieter; Maass, Martin (1991). German Warships 1815-1945: U-boats and Mine Warfare Vessels. Vol. 2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN 0-85177-593-4.

uboat.net

Helgason, Guðmundur. "Karl-Heinz Nagel". German U-boats of WWII - uboat.net. Retrieved 21 April 2015.