External links

• Photos of cruises of German submarine U-54 in 1916-1918. Great photo quality, comments in German.
• A 44 min. film from 1917 about a cruise of the German submarine U-35. A German propaganda film without dead or wounded; many details about submarine warfare in World War I.
• Uboat.net: More detailed information about U-32.
• Room 40: original documents, photos and maps about World War I German submarine warfare and British Room 40
  Room 40
  In the history of Cryptanalysis, Room 40 was the section in the Admiralty most identified with the British cryptoanalysis effort during the First World War.Room 40 was formed in October 1914, shortly after the start of the war...
  
   Intelligence from The National Archives, Kew, Richmond, UK.