Locklin, D. P. (1972). Economics of transportation (7th ed.). R.D. Irwin.
Lua i Stíl Chicago (17ú heag.)Locklin, D. Philip. Economics of Transportation. 7th ed. Homewood, Ill.: R.D. Irwin, 1972.
Lua MLA (8ú heag.)Locklin, D. Philip. Economics of Transportation. 7th ed. R.D. Irwin, 1972.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.