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Dyfyniad Arddull ChicagoNational Research Council. Application of Economic Analysis to Transportation Problems. Washington, D.C: TRB, 1975.
Dyfyniad MLANational Research Council. Application of Economic Analysis to Transportation Problems. TRB, 1975.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.