Sources

Every document, archive and record cited anywhere on Article 121, grouped by who published it. The number beside each is how many facts on the site rest on it. Where the Internet Archive holds a copy, it is linked too; where the original has gone offline, the title links to that copy.

Photographs: 29 Public domain (US government work) · 10 CC BY-SA 2.0 · 6 CC0 1.0 · 6 CC BY 2.0 · 6 CC BY-SA 4.0 · 6 US government work (USAF technical order); Internet Archive marks the item Public Domain Mark 1.0 · 3 U.S. government work, public domain (NASA; NTRS GOV_PUBLIC_USE_PERMITTED) · 2 CC BY 4.0 · 2 Public domain (NASA) · 1 CC BY-SA 3.0 · 1 CC BY 3.0 · 1 Public domain (released by the photographer) · 1 CC BY-SA 3.0 (also GFDL) · 1 Public domain (NASA, via U.S. National Archives) · 1 Public domain (USAF)