Norton, H. S. (1963). Modern transportation economics. Merrill Books.
Lua i Stíl Chicago (17ú heag.)Norton, Hugh Stanton. Modern Transportation Economics. Columbus, Ohio: Merrill Books, 1963.
Lua MLA (9ú heag.)Norton, Hugh Stanton. Modern Transportation Economics. Merrill Books, 1963.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.