National Highway Institute (Estados Unidos), Federal Highway Administration (Estados Unidos). Department of Transportation, Bowman, B. L., Gripne, D. J., Eckhart, D., Capps, C., & Paulk, R. (2004). Design construction and maintenance of highway safety features and appurtenances. [Lugar de publicación no identificado]: National Highway Institute.

National Highway Institute (Estados Unidos), Federal Highway Administration (Estados Unidos). Department of Transportation, Brian L. Bowman, Don J. Gripne, Dennis Eckhart, Christopher Capps, and Randy Paulk. Design Construction and Maintenance of Highway Safety Features and Appurtenances. [Lugar de publicación no identificado]: National Highway Institute, 2004.

National Highway Institute (Estados Unidos), et al. Design Construction and Maintenance of Highway Safety Features and Appurtenances. [Lugar de publicación no identificado]: National Highway Institute, 2004.