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Dyfyniad Arddull ChicagoNational Research Council (U.S.). Highway Research Board. Freeway Operational Improvements. Washington, D.C: National Academy of Science - National Research Council, 1973.
Dyfyniad MLANational Research Council (U.S.). Highway Research Board. Freeway Operational Improvements. National Academy of Science - National Research Council, 1973.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.