Gröner 1991,第4-6頁. Helgason, Guðmundur. WWI U-boat commanders: WalterForstmann (Pour le Mérite). German and Austrian U-boats of World War I - Kaiserliche
Uboat.net. [2015-01-26]. Helgason, Guðmundur. WWI U-boat commanders: WalterForstmann. German and Austrian U-boats of World War I - Kaiserliche Marine -