WRIGHT, P. H., & ASHFORD, N. J. (1989). Tranportation engineering: Planning and design.--Ed.3. John Wiley and Sons.

WRIGHT, Paul H., and Norman J. ASHFORD. Tranportation Engineering: Planning and Design.--Ed.3. New York: John Wiley and Sons, 1989.

WRIGHT, Paul H., and Norman J. ASHFORD. Tranportation Engineering: Planning and Design.--Ed.3. John Wiley and Sons, 1989.