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Dyfyniad Arddull ChicagoOECD. Future Directions for Research in Urban Transportation. Paris: Organisation for Economic Co-operation and Development. Directorate for Scientific Affairs, 1967.
Dyfyniad MLAOECD. Future Directions for Research in Urban Transportation. Paris: Organisation for Economic Co-operation and Development. Directorate for Scientific Affairs, 1967.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.