Não informado. (2002). Journal of Transportation and Statistics. US Department of Transportation, Bureau of Transportation Statistics.
Chicago-referens (17:e uppl.)Não informado. Journal of Transportation and Statistics. Washington: US Department of Transportation, Bureau of Transportation Statistics, 2002.
MLA-referens (8:e uppl.)Não informado. Journal of Transportation and Statistics. US Department of Transportation, Bureau of Transportation Statistics, 2002.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.