United States. Federal Highway Administration. (1989). Manual on uniform traffic control devices: For streets and highways (1988 ed.). U.S. Dept. of Transportation, Federal Highway Administration For sale by the Supt. of Docs., U.S. G.P.O.

United States. Federal Highway Administration. Manual on Uniform Traffic Control Devices: For Streets and Highways. 1988 ed. Washington, D.C: U.S. Dept. of Transportation, Federal Highway Administration For sale by the Supt. of Docs., U.S. G.P.O, 1989.

United States. Federal Highway Administration. Manual on Uniform Traffic Control Devices: For Streets and Highways. 1988 ed. U.S. Dept. of Transportation, Federal Highway Administration For sale by the Supt. of Docs., U.S. G.P.O, 1989.