Cookridge, E. H. (1972). Gehlen: Spy of the century / by E. H. Cookridge. Random House.
Lua i Stíl Chicago (17ú heag.)Cookridge, E. H. Gehlen: Spy of the Century / by E. H. Cookridge. New York: Random House, 1972.
Lua MLA (8ú heag.)Cookridge, E. H. Gehlen: Spy of the Century / by E. H. Cookridge. Random House, 1972.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.