This will be a list of abbreviated archive names or other sources (e.g. book titles) from which I get the sources.

BArch - Bundesarchiv (aka the German Federal Archive)
NARA - National Archives and Records Administration (aka the United States National Archives)
TNA - The National Archives (aka the U.K. National Archives)
Pressac, "Technique" - Jean-Claude Pressac, "Auschwitz: Technique and Operation of the Gas Chambers" (1993)