Não informado. Transport economics. Interstate Commerce Commission, Bureau of Transport Economics and Statistics.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Transport Economics. Washington: Interstate Commerce Commission, Bureau of Transport Economics and Statistics.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Transport Economics. Interstate Commerce Commission, Bureau of Transport Economics and Statistics.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.