National Research Council (U.S.). Transportation Research Board. Committee A3B05. (1990). Travelers' services: Research problem statements. Transportation Research Board, National Research Council.
Chicago-referens (17:e uppl.)National Research Council (U.S.). Transportation Research Board. Committee A3B05. Travelers' Services: Research Problem Statements. Washington, DC: Transportation Research Board, National Research Council, 1990.
MLA-referens (9:e uppl.)National Research Council (U.S.). Transportation Research Board. Committee A3B05. Travelers' Services: Research Problem Statements. Transportation Research Board, National Research Council, 1990.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.