Helgason, Guðmundur. "WWI U-boat commanders: Heinrich Küstner". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 December 2014.
Helgason, Guðmundur. "WWI U-boat commanders: Hugo Thielmann". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 December 2014.
Helgason, Guðmundur. "WWI U-boat commanders: Oskar Steckelberg". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 December 2014.