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Helgason, Guðmundur. "WWI U-boat commanders: Hans Georg Lübbe". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 15 February 2015.
Helgason, Guðmundur. "Ships hit by UC 23". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 15 February 2015.