Harper, D. V. (1978). Transportation in America: Users, carriers, government. Prentice-Hall.
Cita Chicago (17th ed.)Harper, Donald Victor. Transportation in America: Users, Carriers, Government. Englewood Cliffs, N. J: Prentice-Hall, 1978.
Cita MLA (9th ed.)Harper, Donald Victor. Transportation in America: Users, Carriers, Government. Prentice-Hall, 1978.
Atenció: Aquestes cites poden no estar 100% correctes.