National Research Council (U.S.). Transportation Research Board. Committee A3B05. (1990). Travelers' services: Research problem statements. Transportation Research Board, National Research Council.
Lua i Stíl Chicago (17ú heag.)National Research Council (U.S.). Transportation Research Board. Committee A3B05. Travelers' Services: Research Problem Statements. Washington, DC: Transportation Research Board, National Research Council, 1990.
Lua MLA (9ú heag.)National Research Council (U.S.). Transportation Research Board. Committee A3B05. Travelers' Services: Research Problem Statements. Transportation Research Board, National Research Council, 1990.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.