“Gasometerbunker Fichtestraße.” Berliner Unterwelten E.V. Web.
Foedrowitz, Michael. “The Humboldthain Flak Tower.” The Flak Towers in Berlin, Hamburg, and Vienna, 1940-1950. Atglen, PA: Schiffer Pub., 1998. 18-23. Print.
“From Flak Towers to Mountains of Debris Explore the Devastated Ruins of a WW2 Fortress.” Berliner Unterwelten e.V. Berliner Unterwelten, 1 Jan. 2001. Web. 04 Apr. 2016.
Tour 1 – Dark Worlds. Berliner Unterwelten e.V. Berlin, Germany. Monday, March 14, 2016.
“The Mighty Flak Towers.” The War Tourist (2011). The War Tourist. Feb. 2011. Web.