Norton, H. S. (1963). Modern transportation economics. Charles E merril books.
Dyfyniad Arddull ChicagoNorton, Hugh S. Modern Transportation Economics. Ohio: Charles E merril books, 1963.
Dyfyniad MLANorton, Hugh S. Modern Transportation Economics. Charles E merril books, 1963.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.