Zellmer, D. (1999). The spectator: A World War II bomber pilot's journal of the artist as warrior. Praeger.
Lua i Stíl Chicago (17ú heag.)Zellmer, David. The Spectator: A World War II Bomber Pilot's Journal of the Artist as Warrior. Westport, Conn.: Praeger, 1999.
Lua MLA (9ú heag.)Zellmer, David. The Spectator: A World War II Bomber Pilot's Journal of the Artist as Warrior. Praeger, 1999.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.