"German Submarine Warfare 1914–1918 in the Eyes of British Intelligence", LIS Reinisch 2010, ISBN 978-3-902433-79-4*Kurson, Robert (2004).
"German Submarine Warfare 1914—1918 in the Eyes of British Intelligence", LIS Reinisch 2010, ISBN 978-3-902433-79-4* Kurson, Robert (2004).