Knowlton, H. (1941). Air transportation in the United States: Its growth as a business. The University of Chicago press.
Lua i Stíl Chicago (17ú heag.)Knowlton, Hugh. Air Transportation in the United States: Its Growth as a Business. Chicago, Ill.: The University of Chicago press, 1941.
Lua MLA (8ú heag.)Knowlton, Hugh. Air Transportation in the United States: Its Growth as a Business. The University of Chicago press, 1941.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.